I think most people choose the paperback over the hardback because it's smaller, more portable, easier to hold. So the hardbacks go on sale.

When the paperback is release, the hard copies go on sale, even at Barnes & Noble.

Since Amazon pricing of lots of things changes based on traffic, perhaps that's also happening with books?

Bookshop.org doesn't play those games and you can send some of the profit they make to a local bookstore of your choice.

They aren’t, usually, unless there is some weird promotional pricing to offload hardcovers they have in abundance.

Not a burning question, but just a curiosity. Paperback always cheaper at bookstore.