I don’t know if used audio gear is particularly unloved. If you compare it with other household appliances, I bet the resale value would be higher than that of a washing machine (who buys used washers?).
Because some of the parts in my gear are vintage and collectable, I can get more than I paid for them. The midrange compression driver and horn (Western Electric 713b\12025) have nearly doubled in price in the past 15 years. I am sure the Western Electric input transformer (618a) and output transformers (171c) in my amp has also gone up in value. Everything else has probably lost some value, but I’ve gotten plenty of enjoyment from them.