The ultimate piece is not revenue but profit. At some point these enormous investments will have to be earned back. Good luck with that when open weight models are also continuously improving, have cheap providers and for many are already very usable.
The other point to make is that companies are starting to worry about the risks of externally hosted models.
This is at multiple levels if you have a remote API call as a key part of your workflow/software system.
1. Price risk - might be affordable today - but what about tomorrow?
2. Geopolitical risk - your access might be a victim of geopolitics ( seems much more likely that it used to be ).
3. Model stability/change management - you've got something working at the API get's 'upgraded' and your thing no longer works.
If you are running on open weight models - you are potentially fully in control - ( even if you pay somebody to host - you'd expected there to be multiple hosting options - with the ultimate fallback of being able to host yourself ).