jmc

The first jar has a volume of $V=\pi r^{2}h=\pi (\frac{3}{2}{)}^{2}4=9\pi$. The second jar has a volume of $V=\pi r^{2}h=\pi (\frac{6}{2}{)}^{2}6=54\pi$. Note that the volume of the second jar is 6 times greater than that of the first jar. Because peanut butter is sold by volume, the second jar will be six times more expensive than the first jar, for an answer of \0.60\times6=\boxed{\3.60}.