My Delhi home hunt: How much can I really save?

Does price negotiation actually work for new flats in Delhi? I'm looking at a 3BHK in Lodhi Colony, maybe a Green Pike Builders project, and the base price is around ₹3.8 Cr. Honestly, it feels high. What's a realistic percentage one can negotiate down? My parents keep saying builders don't budge much. Also, how much extra should I budget for stamp duty, registration, and all those PLC/parking charges? I'm worried about the super area vs. carpet area trap too, don't want to pay for unusable space. Any advice on managing the all-in cost?