I have a lot of un-made kits. Usually I'll get sucked in because I like the fabrics they chose in the store sample. I have a large stash, but I figure it won't look as pretty if I try to put my own fabrics together. The kit fabrics are usually not pre-cut, unless it's a laser cut kit (usually applique).
There are a couple problems with quilt kits. Sometimes the exact same fabrics as the picture or the store sample are not in the kit - annoying if there's a particular one that got my attention. And sometimes I can't tell which fabric is supposed to be used for certain parts of the pattern.
I've actually never figured out the money part of kits. I'm apparently not very economical. They're probably an expensive way to put together a quilt!