I run the 12 Volt Ofna dark gray chrome top starter box, with power panel. comes with 2 550 motors installed and a battery. I would guess the biggest difference you are seeing in boxes is because some of them come with batteries and some of them dont. I paid $90 at my LHS for mine you can get them for as little as $70 on the internet, but you might pay $15-20 shipping, they are extremely heavy with the 12volt battery installed, I think they ship at 15 pounds.

this is the box that I have but with the power panel and a battery..

http://www.ofna.com/images/st-sb-10248.jpg