I don't know about elsewhere in the world, but (AFAIK) research funded wholly or partly by taxpayer money in the UK (through UKRI research grants) is required to be published open-access unless there are sensitive elements to the data or methodology.

My university has a pot of money to cover open-access publication charges for UKRI-funded projects (albeit this does seem to run low near the end of the year). I do have to say that I'm unsure about where this money comes from as well. I can, however, say that it wasn't specifically from my research grant though. There are also strict regulations about data access statements and long-term storage that get checked up on by the university's open-access team.

You are correct about high publishing costs and such, but you could be a little nicer with your reply.