To a great extent, I think that most instruments in the contra/subcontra range just sound like tubas. While I appreciate the fact that A. Sax, for instance, really wanted to go as low as possible with his saxophones, it's one of those, "Dream meets reality" moments: a contrabass sax costs $25K or so. While I know you can pay $24K for a handmade Meinl, a nice Yamaha is half that.
I can say that the contrabass sax and hyperbass/subcontrabass flutes do make an impression when you see 'em live, it's really hard for me to say that the tone quality is worth the expense. But that's just me.