Alright.....time for me to clarify all the wrong in this thread.
1.) Turkey produces some REALLY nice hookahs....and REALLY crappy ones too....pick it up....you can tell by the weight. Flick the stem a few time to hear the sound it makes...if it sounds like you are flicking an empty coke can...don't buy it.
Firstly, tell them you are buying to use it...not as a decoration. As they will show you the crappy ones (which are honestly made for show)
Secondly, negotiate. But don't be a dick. Be friendly and they will clearly be more inclined to help you.
2.) There is no point to even look for a KM in Turkey because you can get a KM from anywhere. Turkish hookahs are hard to find in the mainstream market....unless of course you are in Turkey.
3.) I have bought 3 hookahs here in Turkey so far....in Istanbul. A Tourist place..The Grand Bazaar. The quality is excellent, and the price wasn't high. So the claim of stay away from tourist places is definitely false. If anything it is cheaper because you have more shops to choose from.