Currently I'm mining litecoin with just one card.
I extensively did my homework (I don't have money to lose) and it came as a high risk, uncertain reward investment.
But I end up checking the pool and RDP to my mining computer every hour or so. It's addictive. I know I'm not making breakeven until 5-6 months form now, presuming the diff will only increase 3% per interval, which is hugely understating it.
But it makes me feel involved and active.
I had a similar feeling playing ogame and checking every hour to make sure no one crashes my fleet.
If I am to add up the cost of time and expertise to that of hardware, I'm afraid mining is a net losing proposition at my scale and resources.
So, I'm guessing the buyers might also be former GPU miners trying to feel they are still in the game. The price, 40-50$ will be written off as entertainment expenses.
There is so much fucking FUD out there that there is a whole legion of newcomers out there that scared to death of buying hardware.
E-bay provides a safe alternative. For Example:
I recently sold a Mining Rig on Ebay:
http://www.ebay.com/itm/100GH-s-ASIC-MINER-Block-Erupter-Blade-Mining-Rig-with-Backplane-and-PSU-/261371727365 for around 1952USD shipping in while around that time you could damn near get an Antminer for the same price which has double the hashing power.
After the auction was over I gave some advise to one of the losers to come to this forum for the best deals on hardware via a group buy. his response was "Thanks for the tip but I only trust E-bay"
This is probably only one of the many reasons why people use E-bay.