Ayyappa Nagar 2BHK, negotiation doubts

Visited 21st Castle Developers' project near Ayyappa Nagar last Saturday. Fed up of renting yaar, finally taking the plunge. Builder quote ₹1.3 Cr for a 2BHK, but not sure if that's the final price. Kitna negotiate kar sakte hain in Bangalore for new properties? Log bolte hain 5-7% is possible, but is it true, especially from an investor perspective? Also, what are the usual hidden charges beyond stamp duty and registration? Don't want any surprises later. Any experience with them?