@quad I don't know what kind of data you're looking for, but I'll just rant on with my own story anyway. :-)

I actually found a "$50 decent" pair for 13 EUR the other year. They were so cheap I figured they'd make half-decent normal headphones if they weren't actually noise-canceling but they might be worth a shot.

They were called Sony PC-130 or PC-13 or something. They weren't even being made any more when I bought them, so it doesn't matter much what they're called. I've used them in the office and on flights, and they cancel (very subjectively) like 50% of airplane noise and 75% of office ventilation noise. I think the really nice Bose ones I have tried years ago canceled like 90% of airplane noise.

The quality that comes with the price has been apparent only in that after a few years, the leather muff on one ear lost its connection to the center, so the foam fluffed out and now that ear is more muffled than the other.

I think the real point of the story may be, buy some really cheap ones, see what they do for you, and then you have a point of reference to explore further. Maybe you could calibrate those audiophile comments on a known pair.

Or, you know, get a $400 pair and they'll probably be $400 decent. :-)