I agree with most of what's been said about the Schultz & Larsen rifles of the 1950s and 60s (the M54J, M60, M65, and M68). They were really excellent rifles in just about every way. As noted, a super-smooth action, extremely fine build quality, excellent trigger, and really superb (single-point cut-rifled) barrels. I don't recall another factory rifle that equaled the S&L in overall quality and desirability.
The M65 was the first of that series to offer ####-on-opening, considered a big improvement. The M65 was a fine rifle and was slightly improved with the M68. The latter had the fully-shrouded bolt sleeve (a mild improvement), had a slightly different floorplate release, and did feature one practical improvement--that being the lowering slightly of the ejection port to permit better ejection. Many M65 owners had experienced ejection failures, with the case being ejected too vertically and hitting the bottom of the scope, with the case falling back into the ejection port (a similar problem to that experienced with the Sako 85).
One thing to check with any M65 is the rifling twist. Some 7x61 S&Hs had the slower 12" twist. For general use (particularly with bullets 160-grain and heavier), the 10" twist is preferred. Barrel lengths varied. Some were 24", some 26", some 25" (my M68DL has a 25" bbl.) and some 24.5", 25.5", etc. I have read that S&L machined their barrels (and they currently state this with their new-series rifles) with a slight constriction at the muzzle (as Anschutz does), and the final barrel lengths may have been determined once the desired length of constriction had been established.
There was never a question about the S&L's ability to handle high pressures. As ‘Boo has mentioned, Weatherby had no hesitation in using a M54J action (dubbed the M56) for his first .378 Wby rifles. A M65 action was tested by the H.P. White Laboratory and was found to withstand 129,000 PSI pressure—undoubtedly well in excess of what a Mauser 98 or similar action would have handled.
The only drawbacks that I can see for the M65 and M68 S&Ls are (1) the rear-locking action that can lead to brass stretching (so a concern only for the handloader) and (2) their somewhat heavier weights. The massive cylindrical receiver, with its very thick walls and narrow ejection port, along with its all-steel construction, make for a somewhat heavier rifle than a similarly-chambered rifle from most other makers. My M68DL in 7x61 S&H,for example, weighs about 8.4 lbs. bare. Non-magnum S&Ls will run a little lighter with lighter barrels.
The issue of brass-stretching with the rear-locking arrangement is real. We get some bolt-compression in an action like this. This is found with all rear-locking actions, such as the Steyr-Mannlicher, Golden Eagle, and others. When I fired some factory Norma 7x61 S&H ammunition (clearly loaded to the max) in my M68DL, I had real difficulty in rechambering the fired brass. On reloading, the shoulder has to be set back, and, if you continue with similar loads and pressure, the sequence of shoulder set-back and firing will lead to case head separation over 5-6 loadings. Excessive brass stretching will occur with continued really stiff loads, so the solution is to stay below true maximum loads and try to go with neck-only sizing as long as possible, or, at the least, partial F-L sizing.
As for prices back in the day, I looked these up in my 1971
Gun Digest, and found the S&L M68DL listed at $485 (US). In comparison, the Weatherby Mk. V was listed at $329, and the Winchester M70 at $170. The extensive hand work with the S&L rifles, such as the single-point cut rifling and labor-intensive fitting and finishing, led to their demise. They were no longer commercially competitive alongside the competition that had gone to far-less labor-intensive manufacturing methods, and their production stopped somewhere around 1970. In the end, only 4,720 M65/M65DL rifles were made, and even fewer, 2,238, M68DLs were ever made.
For those interested, there is the Schultz & Larsen Club website that contains more information about these rifles. Actually, there are two club websites (both links below), with each containing slightly different information. The more recent website is given first below.
https://schultzlarsenclub.dk/language/en/welcome-to-schultz-and-larsen-club/
https://schultzlarsenclub.dk/language/en/project/the-m68dl/
Edit. I forgot that the OP inquired about price. I think guntech has it about right--about $1500 for one in really good original condition. I recently sold a very-good-original-condition M65DL in .264 Win. Mag. for $1700, but that included scope bases and reloading dies. You will see them for less, but, in many cases, they will be rechambered, rebarreled, glass-bedded, or in poor condition. Also, you'll see M60s and even M54Js for less, but they are not quite as desirable as the M65s or M68s, and will be older and have ####-on-closing operation.