Yeah the Germans captured SVT38's and SVT40's and used their piston system to step up from the Gewehr 41, which used (unreliable) gas traps at the muzzle. For whatever reason, the Germans didn't want to drill a gas port into the barrel and instead opted to collect the gas at the muzzle and try to send it back to cycle the action with the G41 and it mostly failed in any kind of adverse conditions. There were two versions of the G41, I believe Mauser and Walther. The Mauser version could be worked as a bolt action rifle, also. Anyway, incredibly complex to make and unreliable so not many got made. The G43 was a pretty big improvement but still had issues. Way overgassed and they like to beat themselves to death, combined with some metallurgy issues at the end of the war it's not uncommon for receivers to get cracked or broken from the bolt slamming to the rear. Aftermarket gas systems exist to tone them down to safely run and not hurt anything. I think estimates are that there were 200,000-300,000 made before the war ended.
Price is totally dependent on condition. For the rifle in the OP I'd want to know:
What serial numbers are there and what matches?
Is the scope an original German wartime production?
The mount appears original, but as with everything German you have to watch out because there's reproductions and fakes all over. The stock is original, but definitely looks refinished at least, if not sanded and refinished.
Typical rifle values range between $1800 for mixmaster Czech rifles to $3500ish or so for all matching original GI bringback rifles. Some museum quality rifles go for more ($4000+). That is without the scope. Original scope and mount is probably worth $600-1000 or so depending on condition. So $3000 for the whole package is potentially fair, but if it's a total mix-master and/or a repro scope, I'd pass, personally. I agree with a previous poster, however, that it would be very nice to see the rifle in person and be able to disassemble it to check numbers, etc...
A lot of people try to sell these things for way more than they're worth and it has driven the "acceptable" price way up. I've always wanted one but struggle to drop the cash people want for them.