I've nabbed a few old console games for a few quid every now and then, semi collectable ones. But I agree, I'm often amazed what some people will pay. Maybe it's not wanting to back down in a bidding war?
In general once more than a couple of people have bid on an item it's probably not going to go for a good price, from a buyer's point of view.
Current example, people bidding over £10 for a used copy of Mortal Kombat X on PS4. It's going for £13 brand new on Amazon, or £8.85 if you're prepared to wait a week from base.com
Maybe ebay offer more ways to pay?