Finding unmolested or unrestored anything Quad is getting harder every year... amazing to see one in that condition, despite as others have said, likely to need much... I did look up references to prices...
"The QRX-9001 had a suggested list price of $1,150.00 in 1977".
I made $4.50/hr as a lifeguard that summer of 1977. Lavallette, NJ... Restaurant work in the fall... college courses, starving student... so playing that Quad version of Piano Man or Eat a Peach LP that I owned, neither was possible.
Back then used record stores were common. I live in Boston. No one wanted the used Quad records, they were cheaper than stereo equivalents in the late seventies and early 80's...
My first stereo; A Nikko NA-550 Integrated & NT-550 FM Tuner, Micro Seiki DD-20 Turntable, Micro Acoustics 282E cartridge and FRM-3 speakers... I remember that Quad was still unobtainable in my budget.
I have to agree about the "brand new", in the box, ;with those eBay finds... Reality is nearly 50 years stored in ambient heat, cold & humidity; with plastics, capacitors and dissimilar metals and solder joints.