Because you have to imagine two scenarios on how the battle gamemode will play out:Why would you not be able to go cav? The light cav classes cost the same as most other classes.
Either you spawn with a ton of money, and you use it all on that one cav class in the start, you die in the start and lose it for the rest of the game.
Or you spawn with not a lot of money, but you never get the chance to play cav because you are too bad at the game.
There is no balance in this