You could get billions for hitting a boss once or twice, so the best way to make money before they changed this was probably to hit every boss you could find once (using one nuke hit on a boss gave you billions). That is obviously not balanced. It was pretty obvious that this was a bug, and if i find something i think is a bug i will post it on the forum.

And i don't really care that other people in here complain that you are not able to exploit a bug anymore ... lol

Does anyone really think that the best strategy should be to hit every boss you find once ?

It also made bases, and money from missions insignificant compared to money from boss battles.