Pune property upgrade: What are the real costs?

Visited a couple of Shree Associates projects near Chikhali last weekend. I'm currently in a 2BHK in Baner, looking to upgrade to a 3BHK, maybe a villa if the numbers make sense. My budget is around ₹1.2-1.5 Cr. I'm trying to figure out the real all-in cost. Builders quote one price, but then there's stamp duty, registration, PLC, parking, sometimes even interiors they push. How much do these add up to typically in Pune? Is it safe to assume 15-20% on top of the base price? Also, regarding payment plans, is a construction-linked plan always better than a down payment option for investors? Or can you negotiate better cash discounts with a higher upfront payment? Already have a home loan, so trying to optimize. Any insights on finding better value in areas like Wagholi or even NIBM Road without paying Kothrud premiums?