It's always a buyer and seller's market. What I see now on various sites are high-dollar firearms and custom guns in the $1500 and up that the sellers are trying to sell for top dollar. Add to that the high-dollar 'tactical' (tacticool) items bought during the panic buying from 2019-2022.
Many of these sellers don't comprehend that all the expensive extras they bought above the stock gun's price are getting pennies on the dollars for these items in the used market. Generally, people don't want a custom gun unless they make it a custom gun.
The AR market is saturated with these guns. Someone bought an AR for $1000, added every expensive aftermarket accessory (over-the-top optics, lights, and 'military' coolness), replaced perfectly working parts with 'custom' parts that added little to nothing other than an attempt to impress others, and now have a $3000 firearm that might be worth 1500 at best.
I know that people buy firearms, spend the money to customize their guns, and believe their updates are worth every penny. But when those same people try to sell that gun, the reality is many of those updates are worth little to nothing to a buyer. Particularly when someone built that gun and acted as their own 'gunsmith.' Who wants to take a chance on someone who built their own gun unless they're a qualified, reputable builder? I don't and I'm not alone.
This is just one of the factors in today's market with used guns.