[carbocation]

Thank you; you're right. It's not surprising that there is some relationship, but what is actually surprising is that the relationship would so closely match an idealized, particular relationship (unitary elastic demand). (And this should have been obvious to me, since the general use of the demand curve is not, by any means, to prove to people that the price they choose doesn't matter.) I'd edit my original post if I were still within the edit window.