I've heard this....about it taking a ton of produce to get a little juice. My sister has one...but she has orchards and vinyards, and usually an over abundance of fruit. She uses it a lot. She brought me some of her grape juice, and it was really close to heaven.
The reason I'm asking, is for the very reason you said JJ....and if I have to BUY produce to make a little bit of juice....it sounds like it might not be such a great deal.