My BPTP Sector 1B deal: Real negotiation limits and hidden costs

Finalizing paperwork for a BPTP investment in Sector 1B, and I'm wondering about negotiation. My experience says builders don't budge much on base price, but what about hidden charges like PLC, parking, connection fees? Those really inflate the total acquisition cost for a 3BHK. What's the realistic discount possible, ya fir yeh sab fixed hi hota hai?