Where do the other prices come from? It doesn't take much Google-Fu to find AIM Surplus. Right now (11/5/2012):
Bulgarian 7.62x54R 147grn FMJ 440rd Can
...from $69.95
Sure, that's buying 2 spam cans of 440 rounds each. $79.95 for one 440 round can.
18 cents a round, even with shipping it's...
The Mosin Nagant is a very well known rifle. Many sites cater to the Mosin Nagant and it's history. The Mosin Nagant currently is enjoying a lot of collector focus, and sites like 7.62x54r.net go into great detail on every variation.
The most commonly encountered model is the M91/30, which...