The real gap between advertised and final property price in Chandigarh

Okay I'll be honest — I completely underestimated how confusing this process is. I'm a first-time buyer, looking for a 2BHK in Manimajra, maybe around 70-80L. Dekh raha hoon X Ecosystem Solutions Llp ke projects bhi. Builders jo rate batate hain, usse final all-in cost kitna upar jaata hai? Matlab, stamp duty, registration, PLC, parking, interiors sab mila ke kitna extra expect karna chahiye? Honestly not sure agar 15-20% extra toh minimum hoga na? Aur negotiation ka kya scene hai Chandigarh mein? Jab builder 80L bolta hai, kitna realistic hai ki main 75L tak le aaun? My parents keep saying 'bargain hard' but I'm not sure if that even works with big builders. Koi hidden charges bhi hote hain jo possession ke time pe hi dikhte hain? Ab samajh nahi aa raha kaise handle karun.