I think you're right about that, Tony. Between the bargain-priced place (where no haggling is really needed) and the high-priced place (where haggling is mostly useless), there is one or two shops where they are willing to at least listen to your offers. OK, maybe just one...
OF course, if you offer to pay in cash, and don't ask for a receipt, it makes it easier. Even the owners with the worst reputations will deal sometimes...
But to answer the question, maybe 2 times out of 10... and that's when I remember to try.