Pianos are not an easy thing to purchase. It's much more like leasing a car as stated by Art_Deco. You need time with the instrument in its own environment before the 'real' effects of humidity and temperature take their control.
Most important quality- integrity
ie) Kawai has the most amazing action out there when they are fresh from the factory. This lasts 6-7 months before it's degraded. I wouldn't pay 50% the retail value for a Kawai after that or before for that reason.
ie) A fresh Bosendorfer sucks. Bosendorfer is known for their warmth and melodic tone, but that's something the piano needs to settle into. This is why no one performs on a brand new Bosendorfer. However, they are worth the price if that's the sound quality you want. Once the Bosendorfers are broken in for years I find their touch to be very deep and can be unresponsive, not sluggish, just unresponsive. However, I think this creates an advantage when creating finger legato.
I'm pretty sure being a Bosendorfer artist entails that they will supply you with a piano for your lifetime. The catch is it's a fresh one, and they replace it when necessary. You actually do the breaking in.
ie) Steinway on the other hand has the most dynamic range of timbres out there. You won't necessarily get the warmth like a Bosendorfer but more clarity and brilliance. On the other spectrum, you can switch from a Mozart sonata to a Prokofiev without switching pianos. Some of the sharpest, fiercest sounds can come out of a Steinway.
ie) Some pianos are very affordable and don't lose their efficiency through age. Yamaha is a good example of this. Falcone being another. Yamaha tends to be sturdy with tunings and handle prepared piano techniques very well
ie) I remember at Arizona State we had a very old Mason and Hamblin in the building. All I can remember is that it was very sluggish in action. Almost as if the double escapement was non existent. Think of a dragging Beethoven op. 53; so slow it makes you nauseous.
Remember housing a 9'4" is a big feat in itself. It's almost better to build the space around the instrument. Acoustically most household rooms will never do the instrument justice, and it's kind of a waste.
Pricing often times has to be done with the dealer/manufacturer directly. They don't just post that stuff publicly; it's more of an elite crowd of buyers.
Hope this helps.