I buy a lot of kits but mostly from yahoo groups by people who bought them and don't want them anymore (lot cheaper) or on clearance from the online shops. The only kit I bought full price was the Christmas Baltimore which I am dying to start. Some of the kits have only the yardage required and some, others have the pcs cut also which makes the quilt top go fast. In all cases kits are more expensive because the makers calculate the cost of cutting. I found the per yard math in a kit to be at least $12/yard.
You honestly have to try one kit and see how you like it then start shopping the smart way for what catches your eyes. I love the fabric choices in these kits and it helps when I need to make a fast gift and don't have time to chose and decide on fabric and pattern.
One more thing I found out when I make a Fons and porter kit they have more fabric in the kit that what the pattern needs. I bought one for my son called the lightening strikes which calls for full but made it little bigger than queen and the fabric was big enough and turned out beautiful.