Greater Noida property: Hidden costs and negotiation pain

Hidden charges in Greater Noida properties are seriously frustrating. I'm fed up of renting, finally looking for a 2BHK in Sector 155. Builders quote one price, then so many extra costs appear – PLC, parking, maintenance deposits. How much can we realistically negotiate? Log bolte hain 5-10% tak possible hai. Any tips on true all-in cost and negotiation tactics?