I've been very lucky selling obsolete miners. There seems to be a huge market of people on eBay who have no idea how much they are NOT worth. Sold Two S5s for a couple hundred bucks each when they were negative profit. Last week sold two A2 110MH Scrypt miners for more than I paid a year ago. Baikal Minis are re-selling over $1000 right now. I even sold two SHA-256 USB thumb miners (U1 and BitFury Nano) for $35 each three months ago!
Buyers seem to enjoy small personalizations that add value like quiet fan mods or additional rubber feet. I prefer eBay for the buyer and seller protections. Be sure you document everything.
Some of these miners have gizmo appeal. I have a large coffee can full of Block Erupters I haven't touched in years. Just last week, I was sorting computer parts and cables from the storage bin and plugged a few of these Erupters in and fired off Multiminer. They still work. It puzzles my sister's boyfriend. Blinky-shiny. I built a small rack for them out of recycled pieces of wood. It's my retro miner object d'art.
Perhaps some people buy these old miners and burn a bit of power in the hope of mining a coin that might be worth something in the future. I think I have PPC somewhere in cold storage. he he.
I sure wish I had the bitcoins I had in my wallet in 2013.
As for me, I'm keeping my Erupters as much as I wish I had kept my Commodore 64. It's unique, like my dad's Ham radio Morse keys and my grandma's Bakelite AM radio, which still works by the way.