Gurgaon property search: How to nail down the *real* cost?

Sector 63A — we checked out an Ahuja Builders project there last month. My wife's priority is a safe neighbourhood and good schools for the kids, so a 3BHK is a must. They quoted around ₹2.2 Cr for a 3BHK, jo starting mein theek laga. But then the 'all-in cost' discussion started – stamp duty, registration, PLC, parking, yeh sab add karke it shot up to almost ₹2.6 Cr. Matlab, it's a huge difference! Also, super area aur carpet area ka bhi bohot confusion hai. It feels like we're paying for so much extra space that's not usable. Has anyone else experienced such a big jump between the initial quote and final price in Gurgaon? How do you figure out the true all-in cost before committing?