RIM must be very confident that nobody will earn more than $1000 from a BlackBerry app in order to make an offer like this. Either that or they are just trying to pump up their stock price for the BlackBerry 10 launch so that the executives can dump their stock before the company goes bankrupt.
Then there are the junk apps that live at the bottom of the list. These come in huge hordes, and are worthless. RIM doesn't want to pay for them and doesn't care about having them. They provide no value to Apple or Google either.
But then there's a comparatively small group of "cool" apps that make everything work. This is the stuff that potential RIM customers notice is "missing". And the authors would love to see an extra $10k in sales, maybe enough to consider a port. And there aren't that many of them -- maybe a few thousand at most. So RIM is betting that if they blow a few million dollars on seeding this market that they'll make that back in extra handset sales in the near term. It might work.
But I don't think they're at risk of losing a ton of money. How many apps actually make that much even on "first tier" platforms?