The difference between a book whose target audience is students vs the general public is often a factor of 10 or more.
Back when printing required physically making plates and limited print runs meant recouping high fixed costs is over. The old justifications no longer apply, but the market hasn't corrected because it is controlled by a cartel.
Most regular books are much more reasonably priced than most textbooks, as well.
The difference between a book whose target audience is students vs the general public is often a factor of 10 or more.
Back when printing required physically making plates and limited print runs meant recouping high fixed costs is over. The old justifications no longer apply, but the market hasn't corrected because it is controlled by a cartel.