Among retro gamers, these types of cartridges are the stuff of legend. No one really knows why — it’s not like it’s the a World Championship cart from The Wizard (those go for $20K) — but it is an extremely hard to find piece of Nintendo history.
The “game” itself is what you’d expect, a test program to check whether a controller is working well, probably used in quality assurance facilities. So you’re not getting a lot of gameplay for your $1051, but if you’re spending a grand on an NES game anyway, that’s probably not your first concern.
[via TechEBlog, screenshots from NES Player]