Earlier quoted context omitted.
Seems like a developer that is getting literally nothing for his app or plugin is more likely to sell it than a developer that's getting some income from it. At the least, the buyer would need to match the current value that the app provides its author.
I don't know. A developer who didn't charge anything from the beginning has more likely other motives releasing his software than making money. But if you already make a little money you may easily fall for a lot of money.
(And yes, I'm aware that's a lesson that really should have been learned by now, if it was going to be learned at all. Alas.)