If you unlocked the two highest towers in the game, use that to your advantage.

When you break a lot of bones, on the screen it shows you how much money the damages cost, however, you get paid for how badly damaged you got.

Keep trying to break your bones on either of those towers and earn money fast.

I had some where around $30,000 from challenges and I'm almost at $100,000 because of hurting myself.

Trust me, it works.