As roshan said, the achievable premium is 50% in sports city at present , that too if u bought 8 to 10 months ago , I own several properties in SC , including one in twin tower. that is the figure that I myself could obtain. Developer keep increasing 5 to 10 % every fortnight in order to keep up with curernt inflation and higher prices for new launches. Generally developer's price rise is reflected after 2 or 3 months in resale market.