Exactly it's supply & demand, & has nothing to do with quality, & little to do with condition, though of course unless it's a vintage or relic model you can expect damage to influence price.
Thing is too with second hand via Ebay etc, you don't get to see it IRL before purchase in most instances, so it's natural for buyers to be deterred if there is any damage, or if the guitar is old.
I think that how much a guitar is worth is very subjective.
If you play it, it feels & looks great & sounds really good it's worth whatever you're willing to pay, or have paid.
On the other hand even if it's a vintage with history, unless you're a collector or investor (or tech), a guitar that's not in working order or that needs some work is not a good buy.
What I can say from experience though, is whatever PRS you buy, new, second hand, from a store, online, or whatever, is that it's going to have superior build quality in any price range compared to most other guitars, will be made with quality materials, & you're much less likely to have trouble down the track with warping or neck turning, as the wood is properly aged & dried, something some are pretty lax with.
The SE singlecut I bought brand new from a store that turned out to be 4 years old, & was clearance stock is the best guitar I've bought, or have owned to date, including a 1975 Gibson.
An Epiphone ES 339 pro I bought only a few months prior to my single cut, is already showing uneven frets, the action & intonation went out when I changed strings (but kept with the original gauge), & the finishing is nowhere near as good as an SE. I suspect the neck has turned a little too; something that doesn't happen with quality wood that is properly aged & honed prior to being fitted to a guitar body.
What I'm saying in a nutshell, is when you invest in a guitar, PRS or otherwise, if you're a player, it's an investment in your passion for playing.
Whether it turns out to be a financial investment, or it depreciates in value is not as important as how much joy you get from owning & playing the instrument.
If you just want an investment guitar, then buy the most expensive vintage or rare guitar you can & put it in a glass case, lest it get fingerprints or scratches on it from being used!
Remember, the 1950's Gibson Les Pauls didn't start appreciating in value until after they'd been discontinued, & even then didn't start to get to ludicrous values until they were 20 years old or so.
So don't expect a guitar to appreciate within the first 10 years of ownership.
Today's bargain could be tomorrows much sought after instrument/investment!
