Gurugram property negotiation: What builders don't tell you

Does anyone *actually* get a decent discount from builders in Gurugram, or is it all a sham? I'm so fed up of renting in South City II, finally taking the plunge. Everyone talks about the listed price, but nobody mentions how much you can realistically negotiate, especially with someone like Conscient. Are those "spot discounts" just bait? And what about all those hidden charges that pop up at possession? PLC, OC, maintenance advances... it feels like a scam. Should I just assume 15-20% above the base price? Change my mind.