Depends on the market. There's an amazing rare book store in the "mall" between the Venetian and The Palazzo here in Vegas. Some of the books you could see. Some you could touch. MOST you had to actually be cleared by the FBI and get a background check just to get the gloves to touch them. So, no.... that's not that amazing. But it's more than I can afford for a book. Unless I could FLIP IT..... <evil grin>
I remember when I was about 10-13 years old. My father received a loaner book from Royal Swedish Library in Stockholm. The book was about 3" thick / 10/14 - It was delivered in a wooden crate that was about 20/20/30 - lots of soft stuff there to protect that book.
It was the only remaining copy of something - bible or law collection - few hundred years old. Hand-written.
My father then put gloves on and set the book on this same table where my keyboard resides now. He took a sheet of certain kind of paper - slided it in between pages and turned it open. Always turned the pages w paper w gloves on. Don't even think approaching that book if you had cold or had to sneeze.
The book was hand-written w font that we call "fraktuuri" - ( "Fraktur" in German ) - and the language was naturally few hundred years old. And my father was reading it as easily we read this writing now.
He worked - as hobby - for about 30 years and then published his work. He was interested in language.
For that particular book - there has never been such thing as "market value" - never will, either.