Not a mauser stock, they had a bit more length and straightness in the shoulder end. Probably it was a high power stock that was adapted with a custom made fitting.
Most of the value is in the pistol and mags, but the stock is a nice addition. I would not worry that people are calling it a bubba job, you are easily looking at 2 to 3 hundred dollars for a functional luger stock, either repro or home made with the proper stock iron. This one probably has some history to it in that it does not look like a chinese repro. Also its likely that it could be restored to work with a high power, but I think its more valuble as it is now. I suspect the custom attaching iron itself would be worth several hundred. A cheap repro for a board stock is about 100.
I'll let others comment on the value of the pistol, offhand it looks to be in good condition with original finish.