Is it the typical sort of sounds that one hears from a contra-alto horn when played - um - "vigorously? And, no doubt, he is playing 'jazz' instead of a Bach 'cello concerto.
I've played more than a few of the low clarinets over the years, but the only contra clarinet that I ever played that was worth more than a bucket of warm spit was a Hovenagel 'BBb' instrument that was still new enough to not be beaten to death. It played as well as my bass, unlike a number of Selmer (Paris) horns that I've had to operate now and again.
The bigger the horn, the more likely that it's to be in poor repair. I've never owned a "good" contra horn (only held a "junker" one bought at a school auction that I later sold, unrestored, for a tidy profit), but I know that if I had cause to own one, I would never let it out of my sight unless it was at one of "my" repairmen. They are too touchy, with pads that are hard to keep aligned, to be handled by anyone other than the vested owner.
If I found a BBb Hovenagel at a good price point, I might grab it. Otherwise, no way, buster...