I buy and sell PCs in my spare time, I only buy something if I'm sure there is a big margin for profit but I don't do it for the money. Even competitively priced I can have a full build sat around for a month or two seemingly with no interest before someone buys it. The opposite is parting it out but most times if I buy a full build I don't get the boxes for the component. Also second hand cases, psus and water coolers are hard to sell and you lose a lot of money on postage for multiple heavy items. Since the fortnite boom last christmas as well it has become harder to sell full build as the market is flooded with garbage PCs that look good to people who don't know any better due to all the rgb.