bit of a necro bump - hope that's ok, Last thing I sold was an I-spy book from a bundle I won, they've been sat on amazon marketplace not selling for ages. Some stuff just isn't worth reselling on there any longer because of the rise in amazon fees & postal costs.
Had a great sale last year (before lock down) , grabbed a My Chemical Romance 7" single from before they went massive, in a charity shop a while back (cost @£4.99 at most) , stuck it on amazon marketplace with photos (whoever added it to the database hadn't put any photos on the listig) & it went for £39.
Best sale this year was selling a film camera I got from a charity shop ages ago (was thinking of getting back into film photography, then got a better digital camera, so it'd been sat in a bag mostly unused), to Harrisons Cameras. Courier picked it up, and transaction went ok, except they initially offered £30 then reduced it to £15 when they'd looked at the camera.
Been looking at vinted lately - it's meant to be for fashion but some people are selling/trying to sell books/magazines and other stuff on there.