I wanted to share what I've noticed on other MMO games that have used the cash shop.

A good example to me is Planet Side 2. Everything is well categorized by type & class in their shop.

They break down everything into at least five sets:
* Infantry Weapons - These are broken down into weapon type (Carbine, SMG, Heavy, etc) and which weapon works for a class (Medic uses SMG, Carbine, and so on).
* Infantry Gear (this is armor, helmets, Camo & badges)
* Vehicle Weapons - These weapons are broken down in teh same way as the Infantry Weapons)
* Vehicle Gear (Similar to Infantry Gears)
* New released items only - If something new came out it goes here.

The Listed weapons include a Compare Stats for all weapons (those unlocked and locked). This helps with deciding what weapon type works for the player.

Once a day they will take one item from the listing and offer it at discounts.

Now a BAD example that comes to me is the Cartel Market for Star Wars: The Old Republic.
A lot of their gear is unorganized and requires some searching to find what you want or need.
You spend to much time searching through the catalog for what you need without a search tag key found in Planet Side 2.

Many of their Big Packs contain randomized gear and items. So Players end up wasting money on something they can't use or don't need at all and more than often don't get what they really wanted.
I call this the CLAW effect: where you pay a quarter to get the gold watch with the claw, but just get those sand marbles instead. Only in this case you're paying more than a quarter.
Worse yet the items BIND to the User, so they can't sell it for a high price on the trade market or send it to their alternate character.

The market even remove a lot of their packs, replacing it with new items and deleting the latter. This is annoying for everyone who really wanted a specific item, but couldn't afford it. But when they finally get to afford it, the item is GONE FOREVER!

Well we all know that the cash shops will really only work with cosmetics and less-powerful weapons. My best idea is a system that would be to have only cosmetics, and then you can "unlock" more cash shop items as you play and level up. So if you're a really basic Chaos Space Marine, you can't have these insanely awesome horns and spikes and stuff, but once you level up you can unlock more and bigger versions, so it still fits to show your level/progress.

I don't have a lot of experience with cash shops as I don't have a lot of spare cash most of the time. But coming from that position I would absolutely LOVE the I believe it was GW2 model where I could potentially earn stuff from the shop just by playing and enjoying the actual game.

DotA 2 and Team Fortress 2 are stellar examples of cash shops, primarily because they focus on customization rather than advantages.

What DotA 2 does right:

• Being strictly related to cosmetics leads to no advantage being gained over spending money, neatly avoiding the Pay 2 Win pitfall.
• All items from the store are lore-complaint (or are supposed to be), meaning that nothing out of place is used and all of the items fit the same general aesthetic.
• Items can be mixed and matched, leading to a greater level of personalization over sets.
• Items have their own color pallette, meaning that they cannot be pushed to look significantly out of place with recoloring.

What Team Fortress 2 does right:

• Items can be recolored, increasing personalization. While this is also something of a con (especially considering the players are supposed to belong to strictly color coded chapters/warbands/ect), if the colors provided are limited to reasonable and appropriate shades (for instance slightly different shades of blue for Ultramarines or a weathering option, ect), then there is no drawback.
• Weapons can be purchased, but they can also be found, earned, and crafted. In the context of TF2 with weapons being abundant and specific ones easily obtainable, this is not a large issue. For that matter, each non-stock weapon has significant drawbacks that go in hand with its bonuses, meaning that regardless of what you're using, you're still balanced.
• Weapon naming and kill tracking for specific weapons.
• Custom taunts. Some may be tied specifically to weapons, but concept remains.
• "Add-ons", objects that follow players but do not impact gameplay. In the context of Eternal Crusade, these could be Servo-Skulls or Nurglings or any number of things.

What both do right:

• Transparency. I cannot stress this enough. One of the biggest things that angered a lot of people about Space Marine's DLC Chapter Armor sets was that it was not very clear on what was being sold. While the pre-rendered graphics of the DLC Armors led them to be a higher quality than the others, the distinct problem was that they couldn't be altered in any way, which frustrated many people (myself included) when we expected to be able to take them apart, recolor them, and other things of that nature. It was especially jarring in the context of Space Marine, which prided itself on its customization and billions of possible armor customizations. DotA 2 and TF2 are both good about telling the client exactly what they're going to get, and also good about allowing the player to preview it as well.

What should absolutely not happen under any circumstances:

• Game Mode DLC. Just don't do it. It always fails, and badly. Not enough people buy it in the first place and those that do become frustrated by the lack of activity. If you want to make new game modes, then package it with an expansion.
• EXP boosts. While they are convenient, they also ruin pacing. They also allow you to access more gear more quickly, and considering that you're already selling -20% bitz and gubbinz in the shop, EXP boosts are wholly unnecessary.
• Too many weapon skins. If a weapon looks different, it needs to act different. TF2 in particular is over-saturated with a multitude of weapons that do the same thing. The Demoman is probably the most extreme example, as he has a whopping nine melee weapons in the same category that all function the same way. This is a severe detriment to gameplay, considering that it is harder to properly assess a threat at a glance when there are so many more things to remember (and many of these things don't even matter).

I played GW 2. Honestly, I never spent any money in the cash shop. Granted, I stopped playing quite a while ago, but at the time they just didn't have anything I was interested in. They backed themselves into a corner with the boxes and keys. It would be more efficient for me to just buy anything I might get from a Black Lion chest, but the few free keys I got gave me everything I needed for the time I was playing.

Commercially, the Black Lion box wasn't a bad idea - a way to get players to drop money on a consumable that could give them resources and equip-able items. As a consumer though, they keys were way too expensive and the contents of the chest simply not worth the prices of admission.

The idea of pay-to-win varies quite a bit from person to person. Over on MWO, some people say the hero mechs are pay to win, even though they're almost identical to the free mechs and in many cases worse. People are set in the mentality that anything you can buy for money has got to be overpowered, otherwise nobody would ever buy it.

Myself, I don't really mind the idea of a sword you can buy and a sword you unlock being the same exact power. Ultimately, everyone can reach the same level. My definition of pay-to-win would be something that gives an advantage that can't be earned through playing the game.

I think you may find that people don't want to buy a sword that is 20% weaker than a free sword when they could just play their way up. If you have any trading system at all, they can find other ways to spend money on the 100% sword so they don't have to earn it. You also have the issue of entitlement. Someone that is spending money on the game is supporting it, paying your wages, keeping the servers open for people who don't play - they're going to feel entitled to a sword that is not 20% worse than someone who doesn't pay a dime for the game.

Those are just my thoughts.

As far as a cash shop goes

1) Integrate it into the game itself. It's irritating to alt tab out and complete the transaction on a website.
2) Give good descriptions of the products. I've run into items, even in AAA games, and had no idea what they were for. This seems like a no brainer, but to a new player, something that says "A key that opens the Infernal Dungeon" means nothing. Add some rollover text to Infernal Dungeon that explains what it is and how the player might get there.
3)Announce a sale before it actually happens. Nobody likes to buy something 15 minutes before it goes 50% off. I think a lot of F2P games are getting better at this, thankfully.

Some items people may be interested in:

HUDs - Oddly enough, no game has ever sold a custom UI. I don't mean one that shows more or less stuff, but maybe the Dark Angel themed UI is different from the generic Space Marine. It has DA colors, DA quotes, the icons, etc. One might have Deathwing iconography or Ravenwing. Basically sub-faction templates. It keeps your UI artists busy, anyway, and should be a pretty simple if you allow for templates.

Custom Avatars - I'm not sure how players will be represented in game (showing their 3d model or with a picture). But if it does use a picture, you could add a handful of free pictures and allow people to select from a wider range of premium pictures.

Voice packs - This might actually be the most expensive to invest in, but allowing people to sound like something other than Generic Space Marine #2 or That Eldar I Shot Three Seconds Ago could liven up the battlefield.

Maybe you could use 'Influence (Factor)' as the name of the monetary resource? It's used in FFG's Rogue Trader RPG for this purpose. You spend your influence and get some stuff. I believe this name could be used for all factions (or even 'Requisition', but that would be quite strange for Daemons and Orks)

I think Requisition is their standard in-game currency. I could be wrong about that, but I recall reading it somewhere.

It also seems kind of odd to buy influence/reputation though. I'm wondering what they are going to call it.

There will probably be two currencies, Throne Gelts/Teef/No Idea for orks and Eldar and Requisition. I can at least see one currency which is IG and one purchased by cash shop.

Guild Wars 2 does well because they let people buy gold when they really want something but don't want to farm for it. Their shop also sells some quality-of-life items. But I have a feeling they're making most of their money from selling Gems which turn into gold.