Upgrading to 3BHK: Lal Bagh mein hidden costs ka chakkar

Lal Bagh mein Vishal Developers ka ek 3BHK project dekh raha hoon, around ₹2.5 Cr ka quote hai. Currently in a 2BHK, so upgrading is a big step. But total cost calculate karna itna mushkil kyu hai? Builder quote kuch aur deta hai, phir registration, stamp duty, parking, even PLC ka bhi alag se charge. Seems like hidden costs sirf possession pe hi pata chalte hain. Construction-linked payment plan better hai ya one-shot down payment? Investor ke liye kya sahi hai?