Lethal, I believe that you contradicted yourself within your own statement. The US has become a knowledge based economy, so let's treat knowledge as a fiscal resource and analyze how much impact teachers have on US "revenues."
The US GDP in 2004 was approximately $11,667,515,000,000 (according to the World Bank statistics). According to the US State Department, in 2004, spectator sports contributed 0.4% to our total GDP. The knowledge-based industries contribute roughly 70% to our GDP. Let's be extremely conservative and say that teachers only have a direct effect on 15% of that 70%, in some form or another. Therefore, teachers directly affect ~11% of the US GDP. Again, this is extremely conservative.
Now let's look at the total dollar figures contributed to GDP, using our percentages.
Athletes/Sports:
$46,670,060,000
Teachers/Schools:
$1,283,426,650,000
As you can see, the impact of teachers on the US GDP VASTLY outweighs that of sports. Therefore, by your own argument that athletes ought to be paid according to their contribution to the money they bring in, teachers ought to be paid much more than athletes.
The travesty is that teachers are extremely undervalued and underratted in America, precisely at a time when they should not be. While Joe Six pack sits around and watches the big game with overpaid athletes on TV, other countries are coveting their teachers and producing large numbers of scientists and engineers. Before too long, America's reluctance to pay teachers what they are worth will result in far greater losses in GDP than athletes could ever contribute.