I think you're right. The issue isn't distance, it's accessibility. Istanbul is very easy to access from most big European cities. Large Turkish communities around Europe and the fact it is a transcontinental city makes it an attractive hub.
If Istanbul is a problem, then you have to balance that with the fact that next year it's at Wembley, and the year after it's in Munich.
Everyone has known for two years that it will be in Istanbul. Whilst I think that the prices of the top two ticket categories are extortionate, I sometimes think that people think that it should be at Villa Park every year with tickets costing a maximum of £20. Even then they'd complain.