The Sega Saturn did a lot worse than the PlayStation outside of Japan, even compared to the Nintendo 64 - only about 2 million Saturns are thought to have been sold in the United States. And over time the disc drives have been failing on them from age. Doesn't help that Sega stopped making Saturns back in early 1998, long before the Nintendo 64 (2002) and original PlayStation (2006) were discontinued.
Combine that with the ever-growing retro gaming hobby/bubble, and now a lot of the working ones are, by this point, in the hands of enthusiasts of the system who don't really intend to sell, or collectors who would want a lot of money for them.