Cost of hair transplant surgery (like any surgery) will differ based on country/location and reputation. It also has to do with cost of labor, overhead, and regulatory/oversight laws of the country (which can add cost).
Wages are a small fraction of the cost in Turkey when compared to the US. Also, there is often not a doctor involved in the hair transplant in Turkey. IF a complication or death should occur, there is no accountability. You get what you pay for.
The costs have to do with overhead and oversight. Many clinics in other countries do not have the same level of quality control i.e often doctors are not even involved in many of the clinics. Also, regulatory oversight is different which affects things like quality of equipment and chances of infection.