Just because something is a harder sell does not mean it's value is less. Yes, in today's market revolvers are not as popular and if you need money quick you might have to take a hit. That doesn't mean that it's value is dinged just that there are fewer buyers. Take a million dollar home vs. a $200,000 home. The cheaper home is easier to sell because there are more buyers in that price range. But due to obvious factors there are also less sellers of big fancy homes so the price can stay up and a seller can usually get fair value as long as they don't have to sell today.
So there's less buyers AND sellers for revolvers right now. It makes it harder for them to connect potentially adding time it take to do a sale. I haven't noticed many deals lately on any guns, revolvers no different.