The last figure I saw was that the U.S. had 57,000 publishers. There are maybe 6 major publishers left. I’ll bet that many of the books you buy come from small presses and you aren’t aware of it.
Yes, there are some small presses that are set up to sell high-value collectibles to fanatic fans and people who are under the usually false impression that they will soar in value. It’s not just King and Koontz. Hundreds of authors are involved and most high-end booksellers catalogs will be full of such editions. Just put signed numbered limited edition books into Google to see what all pops up.
Personally, I don’t ever touch 'em. I can better spend the money on true collectibles or on twenty less expensive books or, even better, on small press books unavailable elsewhere.
Many other small presses have evolved to fill niches that the six majors can’t profitably deal with. It’s become almost impossible for a science fiction author to get a collection of short stories published from a major press. So there are many small presses in the field that print wonderful, amazingly brilliant writers like Kelly Link, John Crowley, Ray Vukcevich, John Kessel, James Patrick Kelly, Paul Di Filippo - to name some I’ve personally bought recently - and dozens more whom the public mostly (except maybe for Crowley) wouldn’t recognize. Some of these are also in limited signed editions, but at maybe $25 instead of $500.
And many of these small press reprint genre books that have fallen out of print.
The mystery field has similar presses, both for new works and old. Crippen & Landru, e.g., has been collecting short stories by many classic mystery writers that weren’t already in other collections in their Lost Classics series.
Other writers are appearing from regional presses who are willing to take chances on local talent that is not being recognized elsewhere.
The number of copies in a print run is going to vary tremendously from house to house, genre to genre, fiction to nonfiction, and even book to book.
So the limited edition small press is a tiny, tiny fraction of the small press market.