The summary explicitly states that it is money earned from the temporary job James and Meowth had at the school. Never mind that you don't reward the winner of a school program (if there even is a single winner, seeing how we're talking about entire classes) with money. It's...indecent ;]Although that is true, I doubt a week of being a janitor can get you as much money as the DP092 summary makes it seem like they have.
There's also the fact that Jessie's team, the Green Group, is currently last, and the summary makes it sound like it's only a matter of whether Team Red is able to catch up to Team Blue's score or not. I doubt that Green still even has a chance of winning.