Well, define "reasonably priced." You can get a "reasonably priced" Earthbound cart, it's all relative. Then again, maybe you just found the right seller who knew it's reasonable value or caught the auction at the right time - outliers do happen.
That said, PS1 was easier to just copy a disc* and play it on a PC or modified console than those that came after it I'll grant you; but, and I might be wrong here as I'm not too familiar, I would think that games from the cart generation are still easier to "just play."
*I think this is a big talking point for PS1 games. Sure, there are rare ones, but that you can literally just copy one to another disc makes their physical presence somewhat of a joke. From what I've seen, usually the "complete" versions of games are what demands higher prices.
edit: To expand on "reasonably priced" a bit: Typically there is the fair-market-value price, and the collector's price. The latter can be gotten if you find the right collector who just has to have it. Most sellers strive for this price, but won't get it. FMV price is what the typical auction will go for, assuming it's not being driven by collectors. Then, you will sometimes find the seller that just needs money, or "... has to sell" for whatever reason. You can get those below FMV.
Yeah, I'm not trying to say people like this (yourself) aren't out there. It's just hard to find someone who will willingly spend that kind of money and risk getting a game that may or may not work for however long. To that point, I don't think this is the majority of people wanting this game, and thus don't drive the market.