Vercel's revenue was 25.5 million in 2022 (according to Nathan Latka who has pretty reputable figures) on a 2.5 billion dollar valuation [0]. They're hyped but it doesn't seem like any big players actually use them at scale, as it's likely much, much cheaper to host on bare cloud providers like AWS, which Vercel themselves wrap (with Vercel also now wrapping the services included in OP's site).

[0] https://getlatka.com/companies/vercel