Rohini mein compact living: Kya kya extra charges lagte hain?

Kitna sach hai ki builders ab bhi last minute pe hidden charges laga dete hain? Humara Rohini mein ek badi property hai, kids have moved out, so we're looking for a smaller, manageable 2BHK in Sector 24. Rawat Construction ke kuch projects dekhe hain. Brochure mein toh sab theek lagta hai, but I'm worried about the 'super area' vs 'carpet area' difference and then those surprise charges just before possession. Kisi ko idea hai, ek ₹1.5 Cr ke flat pe all-in cost, including stamp duty, registration, parking, PLC sab mila ke, kitna extra expect karna chahiye? Don't want any nasty surprises, you know. Is it really possible to avoid these charges?