Gah! a real oddity. Depends on whom you ask. The price is certainly high, and consider the more obscure signatures. I might pay close to $1,000 for it if I wanted it, but I don't want it that much. There's a frame of reference if it helps you.
That's the same seller who thinks a manuscript carbon is worth $1500. To be fair, he believes he has an original manuscript there, but even if he did, his asking price is twice the real world value. So maybe he's got the checklist priced at twice what it's worth too. Though I wouldn't even pay $800 for it myself.
It's worth remembering that multiple signatures on a thing - whatever that thing is - usually make it less valuable than if those signatures were separate. I'm not sure who that book appeals to (at that price anyway) other than a Black Sparrow completist who needs it to fill a hole in a collection.
I have to say that I kind of like the fact that all of his auction photos look like they were taken with a 2003 flip phone in the same basement where he keeps his "lady friend" chained to the water heater. That adds a level of mystery and intrigue.