It's been a while since I worked in commercial trade publishing but I'm thinking the 'industry' is bigger than it has ever been, what with 'everyone having a book in them'
.
You are correct, you hand over the money, get very poor (if any) royalties, and you have to self-promote like crazy to get the word out. Bookshops and chains are unlikely to order from publisher such as this. Public libraries and schools are unlikely to know of the title, and are therefore unlikely to order it.
I self-publish either on the Amazon KDP platform, or via another platform that would suit PB perfectly, depending on the book subject and level of likely sales. I've got a range of puzzle books that are quite niche, and of the 21 titles in the range, 4-5 sell daily. There are a couple in the range that have never sold a copy. Leading up to Christmas, sales will increase as they are great little stocking filler titles. The beauty of KDP is it's free to publish on the platform, you have a marketplace that handle all the distribution, it's always printed on demand so if I never sell a copy, nothing has to be printed. If I sell a few copies daily, the purchaser(s) gets a brand new printed version, that hasn't been sat in a warehouse gathering dust for months. I get paid a commission, for work I did 5 years ago, so perfect for passive income. I have also published what might be described as a 'proper' book (aka, not an impulse purchase like a puzzle book), such as Paul's (!) which I publish via another platform, that means that independent book sellers, chains, libraries and universities can see details on the book, and order it from that platform. It will also be available on Amazon.
If only Paul had done the research, learned how to self-publish, maybe asked in his community and beyond, and took the focus off himself for a millisecond, he might have the book in his hand, with a reasonable commission, as opposed to a lockup full of books to market, package up, post, promote. And be several thousand poorer. Ah well!