And personal experience has taught me even more. Now I can pretty much look at the photos from an ebay listing and spot a problem or identify a unit to not bother with.
Case in point is my TD124--it's an early version (SN 12565) and Thorens made two important modifications after it was released. The Platter Bushings were changed from Nylatron to Sintered Bronze and the Stepped pulley bearing was modified to reduce noise. Had I known then what I know now I would have probably looked for a different versuib. Fortunately, my unit is serviceable, but that adds to the cost. But it's also more valuable, being an early version.
So "how much did I save" becomes the real question and the thing to keep in mind is that when buying a vintage piece, expect to pay more to make it reliable.
So I wanted a new turntable and the table I wanted had to be an upgrade rather than a lateral move. I had some factors that helped me decide. One was that I have Grado cartridges which pretty much rules out VPI because of the hum. Another was that I already owned a nice SME 3009 arm. Granted, I could have sold the cartridges and arm and put it towards something like a VPI but I didn't feel like taking a loss. A Garrard 301 or 401 was considered, but there were two things that the TD-124 had over either Garrard. The Thorens is a belt driven idler (less rumble than idler on motor) and Thorens made a very nice looking plinth for the TD124 back in the day whereas Garrard never did. I wanted a "vintage looking all the way table" and Thorens fit the bill.
Modern tables other than VPI were considered too, but the Thoren's would actually come in cheaper even after repairs.
A lot comes down to how willing you are to do some of your own maintenance verses wanting plug and play.
Something important I learned about the early versions of the TD124 has to do with the Nylatron Platter bushings. My TD124 ran beautifully for about an hour and then it started to slow down. The cause was somebody probably used motor oil as a lubricant which clogs the pores of the self lubricating Nylatron bearings. The bearings lose the ability to self lubricate, heat up from friction and expand until they seize the main spindle. The additives in motor oil pretty much kill the bearing for all practical purposes. Worse yet, Thorens changed the OD of the bushings when they switched from Nylatron to sintered bronze, which makes it difficult to replace those bushings on some of those early TD-124's. I have to send my spindle out to have it repaired properly and will be using turbine oil in the future.
I'm not blaming the previous owner because he probably assumed the problem was with the motor bushings (because that's the usual cause), serviced the motor correctly and listened for less than an hour. In his mind, the unit was properly serviced and ran beautifully. I bought the TD124 chassis, a plinth and had to make an armboard for my SME 3009. By the time I realized the problem, it was too late to ask for a refund or adjustment. Now I can look at the bottom of a TD124 photo and tell what bushing's it uses and whether or not it's worth the bother.
I'm not unhappy at all about the extra expense I've incurred to rehabilitate my TD124 because I really enjoy the way it sounds for the first hour. All said, this turntable (with tonearm, plinth and service) will cost me $2300, which is about what I would have spent on a modern table to satisfy my audio needs. Would a modern table sound the same or better? Who knows and I don't care because I really enjoy what I hear for the first hour. As far as I'm concerned, there's something about these units that makes them desirable and why people are willing to spend the money. I think the abundance of TD124's for sale has to do with the bushings, but at least they are serviceable. Another thing I like is that most of the usual replacement parts are available and that the unit is so goddamn straight forward and simple most anyone can diagnose what's going on.
As far as how much they cost to buy, they've probably doubled in price from 5 years ago, as has the Garrard 301 and 401. So I also view my TD124 as an investment. I doubt any current $2500 table will increase in value in the next 10 years.
But honestly, I don't care about the money. I just like the way it sounds and look forward to using it again as soon as the bushing issue is resolved.
To semi-answer the OP's question, I think the going price is not unreasonable. Especially when you factor in the ability to easily change the tonearm. The ability to upgrade or change the tonearm is a huge factor to me, all I need to do is change the armboard. It affords me the ability to use any cartridge I please down the line. I could even have multiple armboard/tonearm/cartridges and all it takes is 3 screws to swap. I haven't seen a modern turntable in the $2000 price range that offers that much latitude. Seriously a well thought out design. Gotta give credit where credit is due.
Just my 2 cents!
