There is no second hand market, it's just a used primary market.

Before the invention of the internet getting rid of second hand items meant tossing it, or selling it at a garage sale, or for more expensive things taking out an (pretty expensive) ad in the paper. This had a lot of friction. Sellers also had any real idea of what their items were worth. Stuff ranged from wildly expensive to impossibly cheap.

The internet broke this. If I post something too cheap, in seconds a bot picks it up and a person that retails stuff buys it up. Then 30 minute later you find the same item on the same forum for way more. This has a second order effect that these high price posts sit in the forum for long periods of time, so when Jon shows up to sell his table, he sees 50 other tables to $200 and thinks that's an appropriate price. Good deals appear to no longer exist!