I messed up a few months back and used eBay to try and sell an iPhone after not using it for a year or two.
I put up the iPhone for auction only, 7 days.
2 Days in I got an decent offer locally so I agreed to the sale and went to remove the listing.
Turns out, once the auction has been live for more than 24 hours you can only end it if you pay the final value fees of the current bid!
The auction had already reached about £400, as it was past the 24 hour threshold, even though there was still 4 days left, if I wanted to cancel the listing I had to pay final value fees! This meant the ebay listing cost me over £40 in the end and I didn't even sell to an eBayer.