Upgrading to 3BHK: The real cost shock

My current 2BHK in Whitefield is feeling way too cramped now, so we're seriously looking at a 3BHK or even a villa, maybe around Sarjapur Road or Domlur adjacent areas. We already have a home loan, but the price jump for a 3BHK (thinking ₹1.5 Cr to ₹2.5 Cr) feels massive. I'm trying to figure out the *real* all-in cost for a project, say from Prestige Group. Builders quote one price, but then there's stamp duty, registration, PLC, parking, and GST. What other hidden charges actually pop up closer to possession? Heard about maintenance deposits, society formation, etc. Also, this super area vs. carpet area trap is confusing; how much can builders inflate that? Any experiences with these extra costs in Bengaluru, especially for upgrades?