As OEJ says he sold the IP for peanuts but coulda made pooploads by now. There is a lesson there, try not to get to desperate and sell early if you really think your game is gonna be a winner!
I think people underestimate Mike's contribution to the success of Platypus. People talk as though selling the game is the easy bit ( and I'm sure many believe this to be the case ) and that Mike was just smart enough to get a good deal and watch the cash roll in. It's certainly true that he saw a good deal and grabbed it, but he's put a lot of work into making it a success. Yes, it's certainly a shame that Anthony doesn't get more from the success, but it's perfectly possible that he could have ignored Idigicon, sold it himself, and made a lot less than he got from the deal with Idigicon.
And either way, the success of Platypus is going to stand him in very, very good stead for the release of Cletus.