Great rifle but IMO he's way high. You could have a new MkII for $430, same price for stainless. The scope is worth maybe $20. I'd say about $300 even, for that you get the rings and he keeps the scope.
The big difference between the "MkI" and the MkII is the MkII has a three position safety and control feed. I can't remember if the MkI has a fixed ejector but the MkII does. The MkII is more like an old '98 Mauser or pre '64 Winchester.
The MkI has a tang safety which is convenient but not as positive or safe, it's basically just a trigger safety. The MkII safety physically locks the bolt & firing pin - you could pound on them all day with a lead pipe and they ain't goin' no where. Plus it's got a third position that lets you cycle the action to load and unload with the rifle still on "trigger" safety. On a MkI you had to take it off safe to cycle the action.
I've got both, and while I got no plans to get rid of my M77v, I do think the MkII is a worthwhile improvement -- Kernel