Sohna 2BHK hunt: Decoding true expenses

Is anyone factoring in the true all-in cost for ZAK Spaces in Sohna Sector 2? I'm looking at a 2BHK around ₹1.2Cr. What are people seeing for stamp duty and registration out there? Also, the super area vs carpet area difference seems huge; does anyone feel builders like ZAK are inflating numbers? It impacts the effective per sqft. Trying to calculate actual ROI here, so need to account for everything beyond the base price.