The real story surrounding the cost of updating games post-release on the Xbox 360 platform is a murky one. Developers are often unwilling to talk about what it takes to release a patch, likely because they don't want to upset Microsoft. And Microsoft themselves have never talked about it publicly.
When Fez launched for the platform, Phil Fish of Polytron went on record saying that he couldn't update the game with patches beyond the first one he released because it was fiscally impossible. Here's what he said then:
…as a small independent, paying so much money for patches makes no sense at all, especially when you consider the alternative.
…Had Fez been released on Steam instead of XBLA, the game would have been fixed two weeks after release, at no cost to us. And if there was an issue with that patch, we could have fixed that right away too!
Eurogamer reports now that Microsoft has dropped their charging policy for game patches. They cite "multiple development sources" in their story, but they don't indicate any specific names.
The sources say that there will be exceptions. For instance, if developers submit patches again and again after failing certification, Microsoft has the right to charge them. They suggest that this measure will keep developers from over-submitting broken games.
This policy change could open the door for more developers to confidently work with the Xbox platform in the foreseeable future. Of course, letting indie developers sell games without a publisher would also help.
One step at a time, Microsoft.