Jez Corden, who's considered generally reliable in the gaming leaks and rumors community, is pretty confident that game pass is profitable.

And I think separating dev costs from game pass P&L is the more reasonable way to look at it, as Corden explains:

What Microsoft doesn't do is factor in Game Pass cannibalization at the point of funding the game outright. Given that games are being built for a variety of endpoints and business models, sources argued that it wouldn't make sense to put the entire dev costs of titles like Call of Duty or DOOM: The Dark Ages on top of Game Pass — unless the game was going to be fully exclusive to Xbox Game Pass as its only mode of sale and access. Microsoft performs the calculations after seeing how the title performed in the marketplace.