I'd be a little suprised. No one should take Guillermo's claims on things like performance as an unbiased fact. They do make some very impressive things at Vercel, but G is a salesman first and foremost.
I don't mean to say he isn't a skilled developer at all, I phrased my comment poorly if it read that way.
He played a big role in early NextJS development and did great work. My comment was meant as a remark on his public persona, he is very willing to over promise and embelish on how something actually works.
Valuing a VC backed company like Vercel really is a bit of a crap shoot. Even major, publicly held companies aren't valued based on things like annual revenue, profits, or anything that shows up on a P&L.
Vercel is worth exactly what the last person paid for it. There's no real way to come up with another valuation until there's another liquidity event.
Another way to look at it, the last round of investors are valuing in-predictions for future value and have access to potentially private information and financials. From the outside it's not really possible to come up with a valuation to compare to there's, we'd be working with a totally different set of data.