Hi Volkan,
There are two modelshops worth mentioning:
-Mustang Hobby in Kozyatagı
-Murat Yucat(I don't know his shop name)-in Gayrettepe

About prices I can only tell you that I purchase all my stuff (except for minor common accesoiries abroad ...

However there is one item at Mustang hobby,which is actually a late cancelled order by someone;Fiberclassics mb339 rtf less radio gear with a p-120 installed.Ther is apretty good chance you can get a good deal on that one...Of course how you would carry it along would be the Question

Rgds
Eray