I sirt it manually. I just rip a CD, edit its metadata with MusicBrainz Picard then place all the MP3’s in a folder for just the book and then move it to the folder of the author.
Once scanned by audiobookshelf I modify the metadata a bit more and then let audiobookshelf combine the book to one file.
Contabo and NetCup are really cheap. But only if you use their shared VPS option. If you are lucky the CPU steal is low.