My understanding is that while a traditional publisher invests its own resources to market and publish a book with the hope of getting enough revenue to cover their costs, vanity publishers charge the author a fee and then the author takes the risk. With the latter, this allows for less regulation in what exactly is being published.
Now I’m sure that, for textbooks covering (reasonably) broad topics, traditional presses exist along side vanity presses.
I also am aware that out there exist some incredibly niche ‘textbooks’ (some might be a bit thinner than a stereotypical textbook due to their niche-ness but fill the same purpose) over a variety of hyper specialized topics in various fields.
For these hyper niche textbooks (let’s say something you wouldn’t read unless you had a graduate level background), the target audience is incredibly small, so are there traditional presses for these kinds of textbooks?
Surely sales on the textbook will be small since the target audience is so small, which means less of an incentive for a traditional press because of less sales. If they don’t use traditional presses, does this force authors for these kinds of textbooks to use vanity presses or is there some kind of special type of press that deals in these? Or do most use self-publishing?