What they don't tell you about Delhi property's real cost

Okay I'll be honest — I completely underestimated how confusing this process is. We're looking for a 3BHK in Vasant Kunj or Saket for the kids' school, budget around ₹2.5Cr. But the listed price is never the final one. Builders like DLF or Godrej quote one thing, then add stamp duty, registration, PLC, parking, and some 'infra development charges'. Is it common to negotiate these extras? What hidden charges should I watch out for near possession? I don't want any surprises after booking.