Super area vs carpet area: what builders don't tell you

₹1.1 Cr for my 2BHK in Gachibowli last March felt okay then, but now I'm wondering about the super area vs carpet area trap. Mera builder ne kaafi inflate kiya tha, I feel. Salarpuria Sattva jaise projects mein, kitna difference real mein aata hai? Brokers ka role kitna hota hai actual deal mein? Should I have gone direct? What about stamp duty ka final hit, is it always 8-10% of agreement value?