Well, I'd like to have that 10/63 UF. I don't think his price is THAT far out of line. Aren't they $699 new without the extras? Plus shipping/transfer.
EG mags will have half-moon or fishscale looking welds on the spine.
Roughly $20-$25/per on the mags, about $0.20 (retail) per round on the ammo.
Edit: Scroll down for @triplestack3's informative post, he has a far better eye than me!