Greater Noida property negotiation, what's the real ground reality?

Greater Noida mein property prices pe negotiation kitna realistic hai? Shiv Shakti Homes Phase 2 mein ek deal dekh raha hu, but builders kitna budge karte hain, honestly not sure. Log bolte hain 5-10% tak mil jaata hai, sahi hai kya? Aur hidden charges ka kya scene hai, possession ke time kuch unexpected aata hai kya? Investor perspective se, kaise maximise karein deal value?