The Mosin Nagants utilize the 7.62 X 54R cartridge...very much suited to hunting and has the potential for long range lethality. Mosins are very inexpensive in todays market, and there are several varieties. I'm going to make the assumption you are referring to the 91/30? This is a full-size rifle as you probably noticed. There is also the M44 and M38...these are carbine-sized Mosin Nagants that utilize the same powerful cartridge. Russia was the first to produce these rifles, but other countries saw the usefulness and simplicity of the system and began producing their own variants. One of the most noted are the M39 Mosin Nagants which were originally Russian captures from Finland...the Fins replaced the original Russian barrels which resulted in greater accuracy.
As to the cost of Mosins, I have seen them currently as low as 60.00-70.00 for the round receivers and a little higher for hexagonal receivers and others...most likely probably because of the rarity and popularity to collectors. It might be worth mentioning that Mosin sniper rifles (with a bent bolt and PU scope) can also be purchased. Depending on the ranges you anticipate in your hunting, it might be worth a look.
A word of caution, however, if you do choose the Mosin Nagant. Some have said that, "out of the box", they have the tendency to shoot 8" or so above point of aim at 100 yards. There are ways to compensate for this discrepancy, however. Give
www.surplusrifle.com a look. Also, search the Curios and Relics forum here on TFL or do more research on how to manipulate the sights on the rifle.
I have a class 03 FFL, which entitles me to purchase rifles and pistols wholesale, just as long as they are under the "Curios and Relics" classification. Southern Ohio Gun (
www.southernohiogun.com), Classic Arms (
www.classicarms.net), J and G sales (
www.jgsales.com), and Aim Surplus, (
www.aimsurplus.com) all have Mosins in stock, and you can check their price points in comparison to the Big 5 you visited.
There are lots of fellows on TFL who know a lot more about these rifles than I do...but I hope this gives you a little introduction. Also, to have a really extensive overview of the Mosins and their history, check out 7.62x54r.net.