Delhi property negotiation: what's your best strategy?

Negotiating property prices in Delhi feels impossible sometimes. I'm looking at a 3BHK around Panchsheel Park, quoted at ₹3.5Cr by Deals Point. They're not budging much. Honestly, what's a realistic discount one can expect? And what about those hidden charges? I don't want surprises later with stamp duty or PLC; my parents keep saying these add up fast.