400 richest Americans now worth $2 trillion

The 400 richest Americans are now worth a combined $2 trillion, according to Forbes.

That sets a record, Forbes said, and marks a jump from last year's total of $1.7 trillion.

The average net worth of a Forbes 400 member is now $5 billion—also the highest ever. And the costs of being part of the 400 Club rose to $1.3 billion.

(Read more: Gates tops Forbes list again)

But it's the $2 trillion number that remains the most interesting. The 400 richest are now worth more than the GDPs of many nations—and they are worth more than most governments spend or tax.

Here is some perspective on what the 400 richest Americans are really worth.

• $2 trillion is more than the combined net worth of half of all Americans. The bottom half, of course.
• $2 trillion is more than the annual GDP of Italy, Mexico or Canada.
  
• $2 trillion is equal to the Federal Reserve's holdings of publicly traded U.S. Treasurys.
  
• $2 trillion is the estimated size of the underground economy, mostly unreported income.
  
• $2 trillion would fund all government spending through July of this year.
  
• $2 trillion is equal to about two-thirds of all taxes to be collected in the U.S. for 2013.
  
• $2 trillion would pay for all of the existing home sales in the U.S. in 2012 AND2013 year-to-date.

—By CNBC's Robert Frank. Follow him on Twitter @robtfrank.