The labor theory of value maintains that work makes worth. The germ of this post comes from Jane Kamensky, The Exchange Artist (Penguin 2008) at 34. Karl Marx made this belief a pillar of his system but others have questioned (or rejected) the notion that the amount of time invested in a product or service has any essential or privileged bearing on its value.
Hourly billing by law firms borrows from the labor theory of value, someone might propose, because it assumes that the legal services provided are worth the amount of time put into them (multiplied by an hourly rate).
That proposition is false. It may be a workable expedient and a facile proxy for value, but it misjudges the basis for what creates and delivers value to a client (See my post of Oct. 31, 2011: value in use.).