If you do very much color copying in Cleveland then you may have heard of the Xerox Colorqube. The Colorqube line was built specifically with high volume color printing in mind and as a result it can produce prints at a remarkably low cost.
One way that Xerox is able to keep print costs on the Coloqube copiers so low is with a three tiered billing system. Traditionally if you had a color copier there was a cost for a color print, and a cost for a black and white print. If you happened to have any color on a mostly black and white print then it would be charged as if it were full color. With the three tiered billing there is a third option added to the mix called useful color. This allows you to print a small amount of color on a mostly black and white page at a cost much closer to black and white.