Actual property cost in Bengaluru is 15% higher than quoted. Change my mind.

Just moved into my 3BHK in Jakkur last month, an Inspira project. Feeling pretty good but honestly, the final all-in cost was a shocker. Things nobody told me about until the last minute, like OC charges and some weird PLC adjustments. My initial quote for stamp duty and registration was around 8%, but it felt closer to 12% with everything else. Should I have negotiated harder on these? What was your actual all-in cost percentage over the base price in Bengaluru?