It wont work out cheaper than the transfer cost if you add on the fuel you will put in the car !!! 
If you don't use the car at all other than the journey from DLM to Destination, then Destination back to DLM it will work out about a Fiver cheaper, (Put the other fiver saving into the fuel tank), so yes it does. However, take into consideration time of collection, weather conditions, and whether you like driving in Turkey (LHD), and that fiver may not be worth your while.
However i found having a car at hand for the whole week meant we could o furniture shopping, Visit Oludiniz, visit Kirkpinar Restaurant, visit a MMM Migros and do a big shop, and just generally get about. So to me the saving plus the freedom was worth it and more!