Me said:
Depending on condition and rarity, it can range anywhere from about $400 to about $20,000.
I should clarify this a bit I guess.
$20K would be for an all matching sniper rifle with some sort of provenance, like capture papers, period photos of the rifle with the veteran listed on the papers, and a documented trail of where the rifle has been since captured. Here is an example of such a rifle:
http://www.simpsonltd.com/product_info.php?cPath=350_351_357&products_id=35938
$400 would be for a Soviet rework, refinished mixmaster. The Soviet Union captured millions of rifles, and refurbished them over the years in make-work projects. Strip the guns down, throw all the parts in big piles, dip everything in a hot blue tank, slap some ugly shellac on the stock, and throw it all back together until the next time they decide it needs refurbished. Here is an example of a Russian Capture K98 picked at random from Gunbroker:
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=466122141 Just because the uncle served in WW2, doesn't mean he brought the rifle home with him, he could have bought it any time. Hell, it could even be a
Mitchell.
Pretty much every part on a WW2 Mauser is marked with the rifle serial number, the more that match, generally speaking, the higher the value. A all matching rifle these days starts around $1K. Every Nazi era rifle also had manufacturer codes, some codes and years are less common than others, and can increase the value, as can other small markings (that unfortunately can be easily faked) like SS Runes can further increase the value.
Refinishing the rifle, in any way, reduces the value. The folks that pay top dollar for them, want originality.
These prices are also assuming that the rifle is intact, in the original configuration it was issued. Lots of nice rifles were modified to make them more suitable as hunting rifles in the years after WW2, simply because a new commercial Remington or Winchester was pretty expensive, possibly a few weeks wages, where you could pick a surplus rifle out of a barrel at your local hardware store for a few bucks.
A home sporter job, cutting the stock down to a more manageable length, cutting a couple inches off the barrel, mounting a scope, installing new sights, would make the rifle worth even less. Something like this, picked at random from Gunbroker:
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=478810163 And that guy is smoking crack if he thinks that is worth $450.