It should not cost you much, ask before you get in the Taxi and agree a price, it is only approx 4 miles from Calis if that, and if you ask the driver for a return price may get a better deal, or taxi there and slow stroll back through to Ciftlik village and jump on a Dolmus.
If I was gettting a Taxi and making an agreed fare prior to setting out then I would probably £10 or equiv in TL, fuel is much more expensive in Turkey.