Why do you think it's a net benefit for facebook? They probably make a loss if you buy a headset, don't buy anything on the store and un-facebook it.
Facebook is selling at a loss in an attempt to destroy the competition and build another monopoly. They don't care if they don't make a profit now, as they will be able to gauge you later.
Don't buy facebook stuff.
Given the fact one of their main competitors is Valve, I don't think you have to worry about them destroying their competition financially either. Facebook isn't even really competing with them, FB is going for the low end market.
https://www.cnn.com/2021/10/04/tech/facebook-ftc-antitrust-d...