I don't think so. Market makers normally buy before having a specific seller in mind. I think eBay and Amazon's 3rd party sellers transact directly to customers

I don't think so. Market makers normally buy before having a specific seller in mind. I think eBay and Amazon's 3rd party sellers transact directly to customers, and just pay those sites a cut of each sale. eBay only is able to charge that fee (really, it's an economic rent) due to a monopoly enforced by network effects. A classic market failure. (I'm not as sure about Amazon but I wouldn't be surprised if a similar effect was at play.) New car dealerships really don't many any sense and regulated into existence haha. I was referring to used car dealerships