The Red Devils were initially second on the list in 2018 list with Real Madrid third and Barca fourth. In September, Forbes valued the Lions at $1.7 billion, which ranked 31st among National Football League teams.
In Forbes' report, La Liga sides Real Madrid and Barcelona also manage to hold their spots in the top ten among a number of America sporting franchises.
UNITED have dropped from second to SIXTH in Forbes' list of the most valuable sports teams in the world. Forbes states that in 2017, the Cowboys made a profit of $A519 million before taxes. The New England Patriots are the only other team with more than four games in the top 50.
The NFL's Cowboys, who unseated Spanish soccer club Real Madrid for top spot on the list in 2016, were valued at $5 billion (£4.01 billion), a 4% rise when compared to past year, Forbes said in a statement.
That makes the team quite an investment for owner Jerry Jones, who purchased the franchise for $140 million in 1989.
The 49ers rank No. 16 among all sports franchises with only the Dallas Cowboys, New England Patriots, New York Giants, Los Angeles Rams, and Washington Redskins valued higher among National Football League teams.
Each of the top 50 franchises are valued at more than $2.075 billion.
The New York Knicks sit in the fifth spot. They are ahead of the St. Louis Cardinals in Major League Baseball and three other NFL teams - the Kansas City Chiefs, Jacksonville Jaguars and New Orleans Saints. Their value is up to $2.25 billion with an 18% increase.
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