When you are staying longer than 3 months in Turkey, without traveling abroad, you need a residence permit. I used my residence book only in 2004/2005. Since I traveled a lot, it was easier for me to buy a visa every three months. Costs: 10 Euros.
A residence permit costs a Dutch 220 Euros for 6 months. For 5 years: 1.100 Euros.
An Italian can buy one for 60 Euros, valid for 5 years. A big difference.
Next to me there was a guy from Greece, he didn't know this. I am curious what he had to pay.
It's not always easy for Turks to get a visa for Europe, but at least you don't pay.