That still seems a bit high to me, unless you mean older ones? A ten year old Prius is >$10k here [1] and I don't see $5k until I get back to the 2010 model year (14-15 years old, and starting to get a lot less reliable).
Yea, location is definitely a factor. With my zip, kbb.com puts a 2012 Prius v Five Wagon with 120k miles in a private party sale at between $5900-$8200. A bit higher than I thought, tbh. I bought a 2008 Prius a couple years ago for $4,000. I'm thinking I may have just been a little lucky with that deal.
I've found KBB valuses a bit low for used cars since the pandemic, FWIW.
Did you buy your Prius at the beginning of the pandemic? There was a brief period when cars got super cheap (no one was buying anything, sellers were desperate) followed by one where they got very expensive (manufacturing was blocked on missing parts, more people were trying to buy used since they couldn't buy new).
[1] https://boston.craigslist.org/search/sss?query=2014%20prius
[2] https://boston.craigslist.org/search/sss?query=2010%20prius