Mohali possession charges always a surprise

Budget finalised, loan pre-approved for a 3BHK upgrade, but ab toh lag raha hai builders are playing games. I'm looking at a project near Mohali Airport Road, maybe Sector 82. Was quoted around ₹1.8 Cr for a 3BHK, Hercules Ventures LLP ka project hai. But now, possession ke time they're adding so much. Matlab, PLC, OC, maintenance advance, even some 'infrastructure development charges' that weren't clearly shown pehle. Initially my ROI calculations were based on the quoted price plus standard stamp duty. Now yeh extra ₹8-10 lakh ka bill dikha rahe hain. Is this common in Mohali? Kya ispe negotiation possible hai? Ya sab builders ka yahi scene hai? Really frustrated with how the 'all-in cost' keeps changing.