Somehow I was able to place a blue ball even though I didn't have $1000. The effect was to "slow down the game time" and there seemed to be no gain in the end result.
Laser turrets produce money, so when players can buy laser turrets, they can explode in number. The feeling of power inflation is great fun.
However, the game didn't seem to follow the limitation (not the theme), and that was disappointing.