Bangalore 3BHK true cost is always a hidden game.

Bangalore 3BHK true cost is always a hidden game. I'm currently in a 2BHK near Whitefield and thinking of upgrading, maybe to a Prestige project in Sopena Agrahara. Builder quote toh ₹1.8 Cr dikha rahe hain for a 3BHK, but I'm worried about hidden charges. Registration, PLC, parking, interiors ka alag se kitna lagta hai? Aur pre-launch offers ka kya scene hai? Sahi mein discount milta hai ya bas hype hai? Already home loan hai, so I need to be careful with the total budget. Koi experience share karo please.