I love my Barley Crusher and can't remember what life was like before I could crush my own grain. Grain lasts a lot longer when whole and you can buy bulk. If your AG it's a great investment.
It's well worth it if you're buying bulk. Probably not if you're just ordering kits or single brew sized lots of grain unless you just want control of the crush.
They will pay for themselves over time with savings from buying bulk, longer shelf life of grains, and saving on crushing fees (if you are paying those). It is almost universal that you hear folks say they increased their efficiency when they started milling their own, so there is more money savings. Control over your crush means consistency in your brew.
Full (50#) sack of CO grown and malted base pale = $30.00
Going to local HBS for the same grain, by the lb = 1.75 X 50 = $87.50
Savings of being able to buy in bulk and mill your own = $57.50 on your first 50 lbs alone.