How is Turkish economy handling the pressure of so much defense purchase?
Turkey had an estimated military spending of $14.8 billion in 2016. 

A 30% increase would be a $4.5 billion increase. That's 0.5% of GDP. Turkey's government budget deficit was 1.1% in 2016. All else equals, the budget deficit would rise to 1.6% with that kind of increase in spending. Either that or they cut spending elsewhere.