The real negotiation margin in Greater Noida projects

Negotiating price in Greater Noida is way harder than builders let on. I'm currently in a 2BHK in Sector 137, thinking of upgrading to a 3BHK, maybe a villa near Yamuna Expressway for that Jewar Airport upside. My budget is around ₹1.5 Cr. Visited a project by Uppal Chadha Hi Tech Developers in Techzone IV, and the base price for a 3BHK was ₹1.3 Cr, which seemed okay initially. But then the all-in cost breakdown hits you, yaar. Stamp duty, registration, parking, PLC, IFMS charges... builder doesn't tell you upfront. For that ₹1.3 Cr apartment, the final figure was close to ₹1.6 Cr. Matlab, that's a 20% jump! Is it even possible to negotiate these extras? I tried asking for a discount, but they barely budged on the base price, let alone the other charges. Are builders just fixed on their rates now? What's the real negotiation room, like 2-3% max? Has anyone managed to get more off, especially with these rising prices and already having a home loan?