There are many retail stores in Turkey, that sell Apple exclusively. They are owned by the official reseller, PUPA (
http://www.pupabilisim.com.tr). The new Apple stores are actually owned and run by Apple themselves.
A few people in this thread have complained about stores being opened here when they think their aren't enough elsewhere. Well, this is simple economics. Turks love apple products, particularly iPhone and iPads, they can't resist them. Pretty much anyone who can even barely afford them, buys them, then buys them again and again when new models are launched. Turkey's economy has done well in the past 10 years, so more and more buyers can dig deep enough to get their hands on a prized Apple product, so they sell big volumes. It's still a developing market too, and saturation point is still far off.
The only real competitor is Samsung, who are seen by many as a distant second in desirability. This is odd in a country with a relatively low GDP, as iPhones and iPads are by far the most expensive options, more expensive than almost anywhere in Europe. Strangely, other Apple products compare well price wise, Macbooks are cheaper here than in the UK, and compare well with US pricing.
Put simply, Apple are following the money in a growth market where they are already the product most young people aspire to, and Turkey's population is young, upwardly mobile and eager to spend.