Duncan, like many brands today, have MAP (minimum advertised pricing) guidelines. This means that you can't advertise below a certain price, and is why almost everyone has the same price. Now, that doesn't mean they can't SELL it for lower - Duncan can't stipulate that, by law. But this makes it hard to haggle - most places won't go lower because you can't bring in a lower price for them to match, so there's no reason for them to cut price.
There are places that will knock $5 or $10 off, but it's generally gonna be a one-on-one thing.