This looks very similar to http://www.numbeo.com which was also created in 2009. Is it the same data?
What is more, Numbeo seems to be more exhaustive. Expatistan has only 1 accomodation data point (Monthly rent for 85 m2 (900 Sqft) furnished accommodation in EXPENSIVE area) while Numbeo give me information about different size apartments in and out of city center
We started collecting prices for different ones a while ago. We are now reaching the point where we already have enough data to include the new types of housing in the public index.