Furthermore, Steinways are inconsistent in quality; since they are made by hand, you can get two Steinways that are not of the same standard, which is frustrating when you are trying to buy one.
This is a feature, not a bug. The quality is always the same, but differences in the wood as it is shaped through the manufacturing process lend each instrument its own character as opposed to the more consistent but cookie-cutter instruments coming out of other factories.
Steinway instruments fresh out of the factory are designed to be only a starting point. The selling feature of the Steinway design is that it is so very customizable to the preferences of the player. A low tension scale design coupled with a unique hammer construction and asymmetrically tapered diaphragmatic soundboard give the voicing of a Steinway a very large potential tonal palette. It is typically up to the dealer selling the instrument to have technicians that will spend a few (or more) hours tweaking the piano to your final preference. Other instruments are more consistent from unit to unit, but sacrifice that flexibility as a result. It's relatively easy to make a Steinway bright and loud like a Yamaha by shaping and lacquering the shit out of the hammers, but it's quite difficult to take a high tension scale Yamaha and make it dark and moody while still having good dynamic control.
I generally agree with the rest of your comments though.
For someone to say that a Steinway piano which is a low tension scale design is indistinguishable from a less expensive piano such as the Yamaha, a high tension scale design, tells me that someone doesn't play or listen to piano very often. The scale designs make for very different tonalities, volumes, and sustain lengths. The high end piano artists market for Steinway pianos also tells a very different story, considering that Steinway doesn't give their pianos away for free, whereas Yamaha does so regularly purely to gain marketshare, yet the vast majority of touring concert piano players prefer Steinway pianos.