Does Apple pay anything meaningful to ARM? They're a founding member with (I believe still) a significant stake. I find it doubtful they didn't secure themselves a perpetual license when they founded the company, and that seems to be what the Internet believes to be true.

I'm not so sure it's the expensive large chips, made in relatively small quantities, that make ARM the most money, do you have a source? I'd have guessed they actually make more on the billions of small ARM cores that ship every year that end up by multiples in pretty much every device with a battery or power cord. And these, I think, are at the biggest risk of leaving ARM. RISC-V development is mature enough at this end of the market that it's relatively easy for users to transition, there are multiple competitive cores on the market, and there's no concern here about backwards compatibility because these are embedded systems where there's usually not an expectation of having to run user code at all. It will be much harder for the likes of Qualcomm where there's a huge ecosystem built around their ARM processors - but as a share of cost-per-processor, they probably stand to gain the most. Qualcomm is a founding member of the RISC-V foundation after all.