Prices vary,
But I wouldn't pay that much unless it had matching numbers (very unlikely).
The stock could easily be a German replacement (not "aftermarket") especially if there are Waffenamt markings.
neither my 1937 Kar 98k nor my VZ-24 (czech) have an "arms room" disc on the (original) stock. They do have the steel disc for bolt dis-assembly. My 1917 Swede M 96 does have a brass Unit disc in the stock, as does a friend's Swiss K-31. Some countries used them, others did not. Even in countries that used them, no "unit" ID disc in the stock does not mean it is missing. It may never have been there.
All milsurps, and Mausers in particular have risen in price considerably in recent years, more so than the quality of the rifles available warrants. Rifles that were $100 just a few years ago are $300 today, and in some local areas the asking prices are ridiculously higher.
You have a few choices about what you want the rifle for, and depending on your personal desires, and the specific condition of the rifle, and exactly what markings are on it, these will determine whether or not the rifle is a good value for the asking price.
You see, there are three kinds of "value" with respect to milsurps (or all guns for that matter).
Market value - what it will bring on the general market for resale, and also considering the likely change in dollar resale value over time. Appearance and markings are very important, along with general rifle type and how common on the market.
Utility value - How well it does it's job. How accurate it is, how well it operates, and how efficient/effective it is for what you need. And, how well you can use it.
Personal value - What you actually feel it is worth to you. In other words, if you want one of these, because it is one of these, and not just a "deer rifle", or "an old war rifle", then that plays a part as well.
Go check out some online gun auction sites, and some different dealer websites and get a feel for what is being asked for similar class guns. Then STOP, and realize that ther is still a lot of this country where deals are done that is not online. And that differences in prices can be found with some looking. I have not been to a gunshow in the east in many many years, but I know they still have them. Check your state's laws, Federal law allows you to go to a gunshow in a state that borders yours, and buy a rifle or shotgun, face to face from a FFL dealer. IF both your home state and the state you are buying in allow it. If they do not allow Face to Face purchase, then you just have the dealer in any other state go through your dealer in your home state. It will cost more, but it does allow you the opportunity to find the "best" deal. That's the way an internet purchase works as well. From a seller to your dealer's FFL, through the background checks, and all state laws, and then to you.
GI Mausers have become more "collectable" than the were in the past. All the Russian bolt guns brought in in the last few years have kindled a resurgance in milsurp rifle collecting, and (good) Mausers are becoming more scarce, so the price goes up.
Just ask your self, how hard do you work for your money, and how much will you get out of owning the rifle. Then balance that against how likely you are to see another comperable (or even better) rifle later, and how much it will be, compared to how much money you are likely to have at that time.
If you have to drive across town to save two dollars on a fill up, then that rifle is awful expensive. But if, in a few years you will be making enough to buy the rifle, even at twice the price, and not feel pinched (for long), then the rifle, while twice the dollars, is to you less expensive.
