Bought a used headset on ebay for $500 less than a new one, and it turned out to have a small crack. Took it in, and got a brand new one for a warranty replacement. Even better, they let me have a replacement with the connectors I needed, so I didn't have to use an adapter any more.
So I got a new headset of a type I'd always wanted, but never would have bought at a new price.