I've handled new vellum. Actually, it was pin-feed fan-fold vellum forms. The City of Detroit printed out its biannual tax rolls on hugh vellum sheets, one copy for itself, one for Lansing. They were stored in custom binders. Hundreds of thousands of pages per year, at $1.74 a page. And that was over 30 years ago.
I never knew that vellum computer paper even existed until I worked there. I learned a lot of other amazing (or depressing) things working there.