In recent weeks, the price range has risen to $15-$30 for most PS1s -- with a huge premium for the super-desirable SCPH-1001 with the RCA output jacks. I've seen those selling for a low of $30 -- up to and over $50-$60 for perfect samples. You can tell which listings are for the SCPH-1001 -- they usually use the term "audiophile" in the title description.
The 1001 that I recently bought looks to be in perfect condition. But looks are deceiving. Despite the seller's assurances, my unit isn't playing properly (unless you turn it upside down). I think it may have suffered a fatal shock during shipping. It will be replaced. If/when you buy online, make sure you get some sort of guarantee -- and buy from a reputable seller (like I did).
The PS1 music craze may die down in the next few weeks -- but right now, these consoles are red-hot commodities. And even at the $50-$60 level they represent a sound value (another pun). If you have one already, try it. You'll be pleasantly surprised.