@Beverice: I'm fairly certain that the tower price not going down is intended. For instance, if it does go back down, then you can build guard tower on abandoned towerfor 100, get 50 back, sell it and get 55 back, and repeat until you have 99999 gold.
@mrhelpfulman - actually, the difinition of a perfect game in this is having full hp at the start of EVERY wave, not just the last. Otherwise, however you're 100% correct.
I would like to know where I'm getting all this money from. This seems like a fairly profitable venture. And no, he is NOT building cars out of zombie guts.