Sector 79 buyers: Did you face this with carpet area?

I thought I did my homework on my Kiwi Land And Housing flat in Sector 79, but kuch cheezein really surprised me after moving in last month. My 3BHK was marketed as 1800 sqft super area, but carpet area toh bohot kam nikla. Matlab, builders kaise play karte hain with these numbers? I feel like I paid for so much unusable space. Plus, that floor rise premium for my 12th floor unit... ab lagta hai was it even worth it? Should I have looked more into secondary market deals for better actual carpet area at a lower per sqft cost? Kya Mohali mein resale pe negotiation zyada possible hai?