There's nothing wrong with selling things - the ethical problem comes when you buy things and raise prices to sell again - directing the original purchase to the person you've sold to without even taking delivery of the item.
I don't see anything wrong with that. Everyone is still happy. The seller gets his money, and the buyer gets exactly what he paid for. The seller didn't "raise" the price, the buyer offered more than what the seller paid for it.
Would these practices be ok if the seller took posession of the item and then delivered it from his own house?