I would say that in particular, I'm fairly certain I can usually tell the difference between $5 wine and $15 wine, and the $15 wine is usually markedly better.

I would say that in particular, I'm fairly certain I can usually tell the difference between $5 wine and $15 wine, and the $15 wine is usually markedly better. On the other hand, my experience is that it's usually a lot harder to tell the difference between $15 wine and $50 wine, and as often as not, I prefer the $15 wine. Hmmm... as I think on it, maybe there's something more to it than that. Because when I think of those $15 wines, I'm not thinking "generic $15 wine". I'm thinking, "oooo, that $15 wine I really like." That is to say, I'm not sure I could reliably tell you which of a set of random Zinfandels was $5 and which $15. But I know there are certain reliable $10-$18 Zinfandels -- Ravenswood, Renwood, and Rosenblum leap to mind -- that I like much better than anything I've tasted under $10. That doesn't mean that I have liked every $15 Zinfandel I ever tasted, though.