Not necessarily. First edition Harry Potter is about $5000. It isn't special physically in any way other than it is a first edition. So in this case it's historical and literary (I.e. Content) context is valuable. Leather bound 200 year old books can be bought for $20. The Gutenberg bible is expensive not because it is leather bound or because it is old. Those are factors, yes. Bu the value mainly lies elsewhere too.
"Hardcover first edition first printings of this 1997 book have become the ‘Holy Grail’ for Potter collectors. If you find one in the attic, then you’ve hit the jackpot. Only 500 were published and 300 went to libraries. "
I just went online to check with my dealers and I can get all the 7 books for 50 bucks. If I just want the normal editions.
So yeah, you can find a leather bound book cheap, but not if it was released in small numbers.
I can go out and get a Leather copy of Charles Dickinson for 20 bucks. But first edition, first print costs about £4,750.
And if you want to go for the really limited editions you have things like:
(DICKENS, Charles.) BROWNE, Hablot K.
Suite of 29 original drawings for Bleak House. 1853
£95,000