Very good point.

The studies that conclude that tasters are no good at differentiating wine seem to presuppose that price is a good indication of quality to begin with, and when an expert picks a cheaper wine over a more expensive one they fail to consider the possibility that the problem is with that assumption rather than the expert's tasting ability.

Edit: TFA (which I didn't R :) makes the point that there seems to be little correlation between price/qual. But it's worth emphasising this point anyway, I think.