IMHO $815 is a good price for it. MS-64 sales on Heritage for the last year range from $822 - $1300 for PCGS and NGC slabs. Interestingly enough, a beauty in an ANACS slab went for $722 - it looks like someone did a good pick up with that one.
I am not sure if you could reslab it as an error and increase the value enough to justify the re-slabbing cost and flip it.