My 3BHK upgrade hunt: Delhi builders and hidden costs are exhausting me

Since January, I've been seriously looking to upgrade from my 2BHK to a 3BHK in places like Vasant Kunj ya Greater Kailash. Already have a home loan, so trying to be smart with this next investment. But yaar, builders like Chaudhary Realtors are quoting prices that seem non-negotiable. Is it even possible to knock off anything significant from the 3BHK 2.5Cr+ asking price? Every time I try, they just say it's 'fixed' ya 'spot discount already applied'. Then there's the all-in cost scene. Property price toh theek hai, but ye stamp duty, registration, PLC, parking, interiors ka total bill itna zyada ho jaata hai. I'm really worried about hidden charges jo possession ke time pe pop up karte hain. Last time, for my 2BHK, I shelled out an extra 2.5 Lakhs for 'utility connection' and RWA corpus, jo initial agreement mein nahi tha. Is anyone else facing this? How much wiggle room did you get negotiating for a 3BHK in South Delhi? Aur did you avoid last-minute hidden costs? What strategy worked?