Mediocre.
Basically just a rip of the Starcraft Turret Defence games (and it's pretty crummy you didn't give them any credits) minus all the things that make them so fun. First off, the only reason people play those games is because it's fun when EIGHT people team up and try to stop the convoy. Second off, you over-complicated it far to much. It's very annoying to have 200 dollars to spend, but not being able to do anything because I have to wait for some stupid timer to reach 10 before I can build. And finally, no real incentive. At least on SC you get a naked pic at the end for winning which, although small, is better then nothing. I'd say if you want to make it a LOT better, make it so that different people can log on and play a game.