Money laundering. Sometimes people just need a legal place to disappear a lot of money, and those way-too-high listings by third party sellers are part of the system that they either create for themselves or pay someone else to do for them. As long as they (or their launderer) control the listing, they get the money back at the end, and meanwhile if anyone else is stupid enough to buy their way overpriced item, they just buy them one, ship it, and pocket the difference.