"the prices of fruit" doesn't sound right to me. Am I in the wrong?
It is a bit strange. If it were me, as a greengrocer, i would say, "i want to talk to you about the fruit prices."
I agree. Idiomatically, the singular is fine in UK english, and should be accepted
"The prices of fruit" sounds correct to me. To me, it would seem that it is the general prices of fruit in general, not about the price of a specific piece of fruit, though.