I had an entertaining moment at a party a while back where some people decided to play a "Price is Right" style guessing game with the cost of my outfit.
They decided it was fairest to use full price for everything (I never pay full price) to give them a better visual gauge.
How amused was I to inform them that all of their guesses were less than just the retail on my shoes (Zegna chelsea boots, made by Ferragamo). I then hastily informed them that the rack rate for same was more than I in fact spend on the whole outfit on sale...
The correct answer was "no, but thank you." It was an ettiquette question, not a fashion one, and even if you felt she was being rude you should not have been be rude back. It would have cost you nothing to be nice to what seemed like an honest compliment and only would have refected well on you.