Former Microsoft CEO Steve Ballmer raised many eyebrows in May when he offered to pay more than $2 billion for the NBA's Los Angeles Clippers. That figure, however, wouldn't get Ballmer a seat at the negotiating table if he was interested in the Dallas Cowboys.

The Cowboys are the most valuable National Football League (NFL) team for an eighth consecutive year, more than double the average league value, according to an annual survey conducted by Forbes Magazine.

The Cowboys, whose total revenue during the 2013 season was $560 million, are worth $3.2 billion, a 39 percent increase over last year, Forbes revealed on Wednesday.

Dallas, which two years ago became the first North American sports franchise to top the $2 billion mark, has failed to reach the playoffs each of the past four years.

Yet the only sports franchise in the world worth more than the Cowboys is Spanish soccer club Real Madrid, valued at $3.4 billion, Forbes said.

The New England Patriots ($2.6 billion), Washington Redskins ($2.4 billion), New York Giants ($2.1 billion) and Houston Texans ($1.85 billion) completed the top five.

Forbes said the average value of the NFL's 32 teams rose 23 percent last year to $1.43 billion, with each team taking in a record $170 million of national revenue, mainly from league-wide broadcasting and licensing fees.

The Super Bowl champions, the Seattle Seahawks, were ranked 15th with a value of $1.33 billion, a 23 percent jump over last year.