I think I can offer a simple proof. The list of the richest people in the world, and certainly the known billionaires in the world is fairly well established, and is published in periodicals like Fortune or Forbes. Name one person among the richest people in Forbes or Fortune's list of richest people in the world who made his/her fortune from lawyer's fees. Don't just come back to me with a lawyer who also happens to be a billionaire, you have to name one that actually made that billion strictly from working as a lawyer. For example, surely you must agree it's not fair to come back with a name like Robert Rowling, who does have a law degree, and is worth over $2 billion, but that's from being a real-estate and oil/gas mogul (he owns Omni Hotels and is the son of the legendary Texas oil entrepeneur, the late Reese Rowling, from whom he inherited much if not most of his fortune). Robert Rowling hasn't actively worked as a lawyer for several decades, and certainly didn't make his billions by practicing law. Similarly, it's also equally unfair to come back with a guy like Charlie Munger, who is also a lawyer and a billionaire, but is a billionaire because he was one of the original partners in Berkshire Hathaway. Again, it has to be a lawyer who made his fortune off fees.
Here is the list of the Forbes World's Billionaires. You can search through it yourself. By all means, if such super-rich lawyers that made billions off law fees and not through other ways, then by all means, let's hear about it.
http://www.forbes.com/2002/02/28/billionaires.html
Or consider this article from the Wall Street Journal. In the year 2004, the most profitable US law firm was Wachtell Lipton Rosen & Katz, whose partners made over $2.5 million each that year. While obviously $2.5 million is a princely chunk of change, it simply doesn't compare to the kind of money that Wall Street star financiers make. The stars on Wall Street can and do easily make over 10 times that amount in a year.
http://www.lawschool.com/bigbucks.htm http://www.careers-in-finance.com/ibsal.htm
Now don't get me wrong. I don't doubt that there are lawyers that have earned billions of dollars in fees from cases. The problem is that this doesn't translate into billions of dollars directly into an individual lawyer's pocket. Not even close. The fees that a lawyer picks up doesn't go directly to him/her, but rather to the firm, as standard revenue. The firm then obviously has to pay out expenses - the salaries of associates, secretaries, paralegals, and everybody else, the rent of the office space, Furthermore, many of these big-money cases usually drag on for years, so if you want to properly account for what happened using standard accounting principles, you actually have to amortize the fee that you collect over all the years that you spent working on the case. For example, if you got paid in year 5, it's not like the associates who were working under you for those 5 years are simply going to forgo salaries during years 1-4. They are going to demand to be paid every year. So while you made money in year 5, you lost money in the preceding 4 years, and that has to be accounted for. Finally, and most importantly, big law firms have lots and lots of equity partners, and you have to share the profits of the firm with all of them. If you're a partner, and you win a big case, it's not like you can keep all the money for yourself. I think it's plain to see that it would be extremely difficult for an individual lawyer to have put a billion dollars in his pocket through fees. Made a billion dollars of fees? Sure. But to have billions of dollars in his pocket? Very doubtful.