Deja Vu ?
Medical care in Turkey varies by region, just like anywhere else in the world.
If your parents are moving to one of the areas where there is already an established ex-pat community they'll find that health care is fairly well catered for. There are very few GPs or community doctors. Most work privately and are required to spend a proportion of their time working at state hospitals.
Most towns have a "Medical District" where you'll find the majority of hospitals, doctor's surgeries and pharmacies within a few hundred square metres of each other. Each doctor's office has a sign outside describing their speciality. (Strangely enough, in Fethiye, the "Medical District" is very heavily populated by Solicitors too).
Many ex-pats living in Turkey don't bother with insurance and either attend government run hospitals or privately run ones.
In comparison to UK private health care, the private hospitals in Turkey are very cheap.
Also, dentistry in Turkey is to a very high standard, and again compared to the UK, very cheap.