Realistic negotiation on Gurugram 3BHKs, any luck?

Can anyone actually negotiate significant discounts on 3BHKs in Gurugram right now? I'm currently in a 2BHK in South City I, thinking of upgrading to a 3BHK or villa, maybe with Paramount Associates. Already have a home loan, so trying to max out deal value. Is it even possible to knock off more than 2-3% on listed prices? Also, what are the common hidden charges that pop up just before possession? Trying to budget properly and avoid surprises beyond stamp duty and registration. Any recent experiences on this?