i don't understand what a chop cup is...i have some regular cups and balls is a chop cups worth it?
I can easily answer without explaining the gimmick.
A chop cup is a cup which is gimmicked in such a way as to allow you to "hold out" a ball inside the cup with the cup upside-down.
I am a huge fan of both the chop cup and cups and balls, and will close just about any routine I can manage with one or the other...never both.
If I were going to do a combo set, I'd get all three chopped, along with all the balls.
If you are already a C&B man, imagine being able to do a Charlie Miller move mid-air, or holding the cup by the top, with your hand completely clean, and still have a ball held out. The better chop cups allow you to release the ball very subtly, and in mid-air, but most only allow you to release when you set them down.
One other thing about a chop cup is that, since it doesn't need to stack, it can be very innocent looking. For instance, in my collection I have a chopped coffee mug, rice bowl, goblet, opaque shot glass, and even gimmicked a travel mug I've been using for years, and still use to drink coffee out of.