Guy selling a table on eBay decides, "what the hell, I'll try to get $1,000 for this table." Another person selling a similar, easily obtainable table sees this and thinks, "awesome! It's worth $1,000!" He, too, puts it on eBay. Neither one sells, but a third person sees them and says "I'll put mine up for $1,000, too! It's the going rate!" And so on.
Meanwhile, the rest of us find them at estate sales for a few bucks, and sell them for $200. eBay turns economics on its head (at least in the short term), by setting prices based on the hopes of sellers with no concept of what the actual supplies of and demands for the things really are. Of course, sometimes people will bite, and then economics just becomes a matter of chance. And we all want to win the lottery.
Oh, and here's a picture of a six-foot George Nelson for Herman Miller Steelframe unit, new upholstery. A few small tile dishes, too.