http://www.ataturkairport.com/eng/1_f.php?id=105

LUGGAGE STORAGE SERVICES
The luggage storage unit is located on the arrival floor of the terminal and is open round-the-clock. Passengers are charged a daily fee which is calculated after the collection of the luggage. The fees are as follows:
Big size package 15,00 TRY per day
Normal size luggage 12,00 TRY per day
Handbag 10,00 TRY per day
Small size package (plastic bag etc.) 8,00 TRY per day