Sometimes you'll find great deals like that. I don't know if it's done intentionally for short periods of time or if it's a temporary glitch. About 4 years I got a new/sealed Bill Evans' Complete Fantasy Recordings box set for $27.00 delivered from Amazon, not a marketplace seller.
Whenever I'm interested in something, I put it on Amazon's wish list and check it regularly. It's surprising on how the price can fluctuate on some items.
Both the things I put on my Amazon wish list skyrocketed to hundreds of pounds within days
MG