When will we ever hear turntables demoed fairly?

Still, we should be able to compare a few table/arm/cartridge set-ups with the same amp/speakers and comparable if not necessarily the same phono stages.

That still renders the results misleading. System matching is the crucial element in getting component audio to "sing." Sources, preamps, amps, speakers, and of course the cables in between each. But LP decks are a whole different can of worms. Digital sources generally have nearly the same output impedance and output voltage. You can compare players and music servers pretty much with impunity. You can even then leave these players in place and swap various DACs in and out to look for further improvements.

There is no such equivalent with LP decks. They are truly "analog" electromechanical devices which retrieve the physical source at a microscopic level (the record groove). There's no way to perfectly adjust every aspect of VTF, VTA, azimuth, and tracking angle for every cartridge, and even if you could, there could be various levels of damping fluid for tonearms so equipped, various mats that work well with one but not another, footers, platforms, power cords, cabling. And if you change the phono stage, that by itself doubles the complexity with each swap.

So John, what do you suggest?

inna:

So John, what do you suggest?

I was trying to answer the original question, "Why don't we hear turntables demoed fairly?", not to provide a solution. Ironically, the solution is probably the foundation of Audiogon itself. Audiogon was a high end classified ad website before it had forums and member system profiles.

Because there are so many interdependencies in an LP playback system, it is better to evolve the system over time, making one change at a time, do in-home demos where you can (e.g., phono stage, mats, cables, etc.) and when you get a bad match for a cartridge, put it up for sale. If it's a desirable cartridge with minimal time on it, you might recoup 80-90% of the purchase price. Audiogon classifieds offer many such items.
 

We'll leave it at that - there are seemengly no solutions. Except that one may try all possible combinations in one's system in the hope of finding subjectively the best one. Funny, isn't it? 
A few days ago, I was listening to the advertising video on Pear Audio website. Hard to get into the sound through all this digital. However, I had an impression that the turntable itself and probably the arm were very fine but the cartridge and the speakers were not quite by comparison. Electronics appear at least good. Point is that you can hear the table's performance regardless of whatever else is there. Just because it is difficult doesn't mean that it cannot be accomplished. I might've been somewhat wrong in my example, but one thing I am certain of - that table is excellent. When the foundation of the source is good you know it.
Good luck to everyone on their sound quests.

Another example. Go to Purist Audio Design cables webside, there are some videos of systems's demo. You can hear clearly that those Tidal speakers and electronics are inerior to Classic Aidio/Atma-Sphere system, even though the Tidal system has a digital source you can differentiate. By the way, the analog front end in Classic Audio/ Atmashere set-up was not up to the task. Not bad but not good.