I see your point and personally I would love to sample older MM carts from the so-called "golden age" but I’ve found that my efforts haven’t been too fruitful (haven’t seen the magic yet). The carts that interest me - a Grace Level II for instance - are pretty old at this point. its like a car. air cooled porsches are wonderful and superior in some respects to a more modern car (tank like build quality; seat of the pants thrill). but they’re old and you need to know a thing or two (or spend a bunch of money) to get them fully "sorted." On the other hand you can buy an artisanal car that takes the best of vintage technology and mates it with modern design and materials, like the Singer Porsche. But of course you’ll have to pay a lot for the service. I would love to drive a Singer 911 but it’s out of my range.
All vintage carts in my collection are old, but NEW, some of the even sealed (NOS), you have mentioned the Grace, i have nearly all Grace LEVEL II and F14 top models with all the exotic cantilevers. These are fantastic cartridges. An opened item does not require any service at all, i don’t service an old cartridges. I have no idea what do you mean by servicing an MM cartridge ? All you need is a brand new stylus wich you can change by yourself, and we don’t need a service for this operation. I am buyin spare styli too. I have NOS factory sealed styli that i will open myself when needed. A fear of dried up or softened suspension is a myth for most for the well know top of the line vintage MM/MI and MC, except for some notorious models that must be avoided.
I do not miss my two ZYX at all, because some MC cartridges like Fidelity-Research FR-7fz, Grace ASAKURA ONE, Miyabi MCA ... had a much bigger impact. I even bought Ikeda 9 III and Miyabi Standard ... and even if i will add many more rare vintage MM/MI in this list the total in USD will be lower than retail price for one ZYX cartridge. But the experience with so many cartridges is far more important than a wish to own something very expensive and pretended to be the best ever.
For this reason i’m asking for the background of a person who’s buyin the most expensive cartridges in the world. If this person have a decades of personal experience with many top of the line LOMC or MM made before ZYX brand was registered, and the ZYX is a result of his personal research i can understand it.
But if a person comparing one ZYX to another ZYX and dealing with all these cartridges for years i just don’t understand the hype. I’ve been there with two ZYX models that was extremely expensive for me (personally) and Premium 4D SBII was better than Airy III with silver coil. Dealers always pushing a new models and ready to offer "special prices" or exchange/upgrade. They can do all that tricks and you’re hooked. One day it’s time to say "ok that’s enough, i’m quit" (imo).
There are many cartridges that sounded so much better/different than any ZYX i have tried in my system (and all of them are much more reasonably priced for a "normal" person). The same dealers in the US can offer Miyajima for example.
Anyway, it’s all about personal preferences in sound.