PS-X9 was difficult for anyone to have spent much time in front of considering that maybe 250 (max) were ever built for the world. It was a "statement" piece that Sony had hoped to get into the broadcast market. I have seen pricing all over the map - one in Germany was listed a few years ago at 18,000 Euro but I doubt it sold. Most common pricing was in the 8,000 - 12,000 USD range.
I've owned mine since 1983 ... and have used it since 1981 at audio shows when I was a product specialist for Sony. It truly is a magnificent beast and the built-in HA-55 head amp is incredible. Mine was mounted with the XL-88D MC (which unfortunately suffered a broken cantilever that was going to require a second mortgage to repair).
I do not ever recall being able to switch tonearms on this - if someone has, it's a Frankenstein.
Nearly 40 years later and it still keeps perfect speed and sounds incredible. Mine has the dust cover, a second high-density platter mat, plus the hardwired stop/start remote (socket can be wired into a broadcast control board)
I have thought of selling - and targeting the $10k range - but at 32Kg for the table alone, shipping gets expensive. You'd be closer to 40Kg as you would probably want to crate it. The original packing was very good, but mine had deteriorated over time - and for the longest time, I had no intention of selling.
There were a couple of reviews out there. When I find them, I will post the links