Vercel charges low/mid five figures for their enterprise plans, which essentially comes with higher usage limits, some security features like SSO and IP blocking, and an uptime and support SLA. This hardly seems worth the additional cost?
It seems like they need a much better solution somewhere in the mid-tier--Vercel is great to get started on projects, but if you basically need to go from small project to 5 figure bill without much in between, it hardly seems to make sense to use for a project that is going to scale.
Higher usage can be purchased separately from Enterprise, not as cheap as the initial plan, but far from 5-figures: https://vercel.com/docs/limits/overview#additional-resources
So really we're mostly talking about SLAs. I think "we absolutely need an SLA" seems a decent way to differentiate between small businesses and enterprise businesses.