There is a big premium for "never hinged" as well.
If you were hoping to purchase that stamp, with some searching I think you could find one with the same centering as shown in the picture for $10. $20 and some time spent looking would get a very nice example. A pretty, never hinged stamp would probably be $50 (and up).
They are for sale everywhere, so you could probably get a good idea of the overall market by looking at
ebay. (Guessing...I didn't specifically look to see...)