I did the completed the bouncy bouncy level and got 46,843 coins, then I did the eye tower level and only got around 38,000.
So if you need to make more money do the bouncy bouncy level.
Make sure you use wall blocks, make it so there are two very long passages to your base, then keep selling the last block at the end of one passage so that all the units go towards it, then when they get near it place on again to block up that passage. That way, enemy units just keep to-ing and fro-ing, giving you loads of time to shoot them down.
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