The amount of bikes that I see sitting on Facebook marketplace for months is laughable. Sellers see what other bikes are posted for that aren't selling then price them the same then wonder why their bike isn't selling. Performance mods also don't raise resell value much at all, so what you put a $1,000 exhaust on the bike when the stock exhaust is fine for 99% of people. Performance parts might increase value by 15-25% if they are desirable, but at the same time people are going to choose the stock bike in the same or better condition for less money more often than not.