Answer
No, it is not a good deal.
Work Step by Step
Area of 12 inch pizza =
$\frac{22}{7}\times 6^{2}=113.1 inch^{2}$
Area of 8 inch pizza =
$\frac{22}{7}\times 4^{2}=50.3 inch^{2}$
So, total area of 2 such pizzas = $50.3 \times 2 = 100.6 inch^{2}$ which is still smaller than the area of the 12 inch pizza.
So, it is not a good deal.