Your comment is interesting. I was thinking about it, and felt I could add some light. Jelco made excellent tonearms and parts for many years, their own and for others.
Micro-Seki, '80s era AR, Japanese Mfgs., also parts, and headshells. The last Jelco arms perhaps went to Ortofon as their arm used Jelco hard parts. I understand these were excellent. The price is no surprise, if you can find an '80s tonearm and its original price. Put it through an inflation calc. and you'll be amazed. The tolerances and precision required to control a stylus without negatively affecting the sound have not changed, and is not easier today than yesterday. Precision bearings are what they are. Skill of manufacture are a necessity, full stop.
It's interesting that many turntables on the used market favored for use/restoration by folks use separate tonearms. For many years '60s into the '90s, separate record player chains, were popular with the higher end phonographs. My AR 'The Turntable' came with an AR branded Jelco mfg. arm. It's a good arm and was excellent for the carts of the era. Like many folks who upgraded their table by buying an armboard and arm, I purchased a Jelco 750D, an excellent arm expanding the types of carts into the medium weight range allowing me to play with more different carts. Of course it wasn't one of the high end pieces of jewelry, and a bit under rated. Scarcity in the market raises prices, it's just what happens.
Once you understand that matching a TT and Arm with the right cart. makes a huge difference when you get it right, I'm not sure going back is in the cards. Vintage and New TTs sold without arms continue this. The loss of Jelco to the industry is very sad. The new Sorane seems to be a good replacement. Used arms are out there and worth watching for.
This is not meant to be a rant but I think the context of precision manufacturing by people working by hand is unappreciated in todays, 3D print world. Hope this helps gives some little bit of insight. FWIW, YMMV, etc.