By conventional measures, Big Law firms are some of the most profitable businesses on earth.

The average profit margin for the Global 100 is a lofty 39 percent, according to data published this month by The American Lawyer. The highest profit margin in the group, which goes to Quinn Emanuel Urquhart & Sullivan, is almost 68 percent. That’s more than three-and-a-half times the net margin of tech giant Apple Inc., and over nine times that of Warren Buffett’s Berkshire Hathaway, based on each company’s returns in the last quarter.