Would you buy a second-hand child carrier?

This isn't an attempt to flog one, by the way. I've had our old rear mounted child seat on eBay for just over a week now with no bids and no watchers, which is kind of a surprise given that it starts at only a fiver. Are they like helmets and the general consensus is that you'd be out of your mind to get one second hand? If it doesn't sell I just plan to nip down the road and give it to the charity shop, unless it's something that no one will buy, so I'd like to get some idea here.
Specialized Roubaix Elite 2015
XM-057 rigid 29er
XM-057 rigid 29er
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On the other hand I've got two rear mounted seats and both were second hand. Although I didn't go through eBay - just local classified ads. Maybe it's the "sight unseen" thing people don't like?
XM-057 rigid 29er