Is it true...?

[Bluevoss]

...that if you fail a map enough times, you start geting cash bonuses when you try again?

So says the manual, but I've not seen it yet.

How many starts (if true)?

[Alexander311]

This depends on your difficulty level. If you are playing on Casual or Very Easy, then yes. You get an extra $1 every time you fail if you keep trying to play the same map over and over.

[Bluevoss]

Aha. That's what I get for being historical. Thanks for the answer!