Actually, I think we should try to make clear how this exclusive thing works in practice.
As far as I know, there aren't any exceptions - each developer will pay its own development costs down the line, unless the game fails miserably and they still get away with it. The publisher only gives them an advance which they will substract from the sales revenue to recoup their investment.
I'd rather believe that an exclusive deal means that the contract favors the developer a lot more then usual. There are many possibilities: they can retain IP rights, they have a bigger royalty percentage, MS requires a lower amount of licence fee per games sold; and these can all apply to inhouse development teams like UBI and EA as well. Keep in mind, if MS asks $5 less per unit, that already means an extra $5 million pure profit for a million selling game. For something like GTA 4, we're talking about as much as 30-50 million.
Smaller, independent or semi-independent game studios can also negotiate better terms for the calculations of how MS gets back its advance. In most cases the publisher gains a larger percentage of the revenue then the developer who did the actual work, just because they've presented the advance to fund the actual development, and it's still a better deal then a straight bank loan. But if a title has achance to increase the console's value for the customers, maybe even become a system seller, then I'm sure that MS or Sony is willing to give up some of their profits in exchange, just to secure the title.
So the point is, that I can't really believe MS and Sony throwing out millions to developers and not taking it back at all, that sounds unrealistic.