Well for value if in original condition and has not been messed with, P. Peterson in the 2020 new 9th edition of The standard catalog of Military Firearms has the following.
German receiver converted to .308 marked 7.62 on receiver over german markings Exc 500, VG 375, G 300, Parts/Fair 150. Now the Fond du Lac, Wi, largest GS in WI, yesterday had a real nice one that I missed at $625. I mean it was great condition. I just went up the wrong isle 😕
Now a Czech post war made .308 Nato Israel mauser is listed at EXC 600, VG 525, G 400 and parts/Fair 250. There were two just really beat ones at $300. CAI Guatemala junk. No takers due to sewer pipe bores and poor stocks. Dogs that should have been 150 for the bolt and screws.😒 See page 247.
I would value an original German Mauser with receiver markings intact, restamped 7.62, as more valued than a post war Czech rifle. I would have been happy to pay $650. It was a better example, the best I have seen in a long time-- but fate had it that it was not to be. Most have the German markings scrubbed and new Israeli receiver markings applied and that is more like the book value. A K98k with Intact German receiver markings are always better than the scrubbed version no matter what condition the barrel is!
As for price there are so many factors- state laws and regional rarity are big factors, then you look at the rifle type: See my SRF post:
On that example you saw the stock was an Israeli replacement not a correct original German stock and that really hurts the value more toward what is mentioned in the book. Figure $250-350 to find a German stock, then maybe sell of the Beech stock to recoup about half value. Now an Israeli marked K98k bayonet is nice, really nice; and an Israeli grenade adaptor is another plus-- figure the two are worth about $160/200??? The israeli marked leather sling is also a plus. So if you could live with a odd ball stock, I'd say $600 might be fair if the bayonet was nice in a scabbard and the launcher was in its web case?? That's about $400 for the rifle, then you find a replacement German stock. Others may think I am nuts, they would rather have an intact RC or bring back K98k. Most do not favor the NATO round.
Best is an Israeli marked German 8mm K98k. NO CONVERSION. That is big bucks. You need more details, a true German WW II grenade launcher is also big bucks. Are the extras German marked or Israeli marked. It's better if the bayonet is Israeli marked and way better if it is a non Israeli grenade launcher. A true K98k marked German sling is worth more that an Israeli marked sling. So check out the markings on the extras. The striper clips are just garbage to throw out. Look at some of the Empire more current sales in that link- it provides a sold price , and photo, as well as the year of the sale. that can get you into hand grenade range for value. I guess how bad do you want one, how many do you see at gun shows in your area, and how much cash do you want to play with. It is always better to see a rifle in person rather than an on-line auction with fees, shipping, and FFL transfer fees. All factors to consider.
If you got a job and make 40-60 bucks an hour, you want it, then walk in with a hand full of $50 bills and deal. Cash talks, times are hard. I assume the extras are all Israeli marked. So maybe start at 500 and go up, but I would figure you need a replacement German K98k stock -$350 from what you consider a value is. Use it as a bargaining chip. It just depends how hungry the shop is for cash, and how fast surplus junk sells in your area??????
Be sure the receiver codes are clear and crisp, an example worth a restoration to find a correct German stock. You might want to check headspace,if going above $600.