Triple cost. 1 Melta bomb = 120 2 Melta bomb = 360 But, I must say that melta bombs are very useful when you have to destroy a vehicle well defended or when you need to destroy a vehicle before it deploys the troops it carries (premades transports are very dangerous). I must say too that since patch 23, it's much more hard to survive as fire dragon. The knife doesn't work as well as before, and when you're hit at melee, you can't fire your weapon. A power sword advances faster with the fast attack than the FD walk when melting (and faster than an eldar running if he doesn't have an evasive roll ready), so the best class to stop meltas are the JPA, for sure. I was able to dance around exploding tanks before, now I must do it in 2 or 3 tries sometimes (to be a lone wolf aproaching to a transport spaming enemies doesn't help).
Fire pikes are coming, I wouldn't count on pistols, because they are essentially fusion pistols mechanically.