Higher discounts for lower-value work?

A co-panelist recently mentioned as a cost-control method the practice of requesting higher discounts for work that the law department deems to be of less value. There may be a kernel of a useful idea in that practice, but I am doubtful.

Perhaps different discounts make some sense if you use one law firm to handle both the valuable work and the less valuable work, but otherwise it would makes more sense to choose a less costly firm to handle the lower value services (See my post of Dec. 26, 2008: third metapost on discounts, with 12 references.).