The Dallas Cowboys are now the most valuable franchise in professional sports, as Forbes estimates their worth at $4 billion.

Jerry Jones bought the team in February 1989 from H.R. "Bum" Bright for $140 million. Factoring for inflation, the value of the Cowboys has since jumped 1,382 percent based on Forbes' new valuation.

Rounding out the top five most valuable NFL teams are the New England Patriots ($3.2 billion), Washington Redskins ($2.85 billion), New York Giants ($2.8 billion) and San Francisco 49ers ($2.7 billion).

The average NFL franchise is now worth $2 billion, a 38 percent year-over-year increase due to the increase in national television rights fees.