Well most miners could be considered used. I'm not sure why people buy from ebay while they are cheaper in China. Yes it takes longer but is +50% price justifying few days of delay? Maybe if the seller is from your country and in the end you don't pay VAT...
For some people it is a lot more convenient to pay with a credit card than it is to pay with Bitcoin. For some, buying coin isn't all that easy. It's also a way for people to buy equipment without having the money up front. It's not a smart way to do it, but thats how a lot of people use credit cards. Buy now, pay for it later.