Saqib, price difference is due to sequence of possession and house construction. Sector A is ahead of all with 30-40 ten-marla houses constructed or under-constr. In C-1 two houses just started. In B2, no activity as yet.
Bottom line: buy 10 marla, good location plot in C-1 for about 6-6.5 million and build house after 1.5 years. By that time, your neighbourhood will be well-populated.