The Denver Broncos announced their new stadium will be privately financed, but across the 5 major sports leagues, only 20% of facilities are actually privately owned.
A scholar of sports finance explains what "private" really means (it often uses tax dollars): 

The Conversation
Broncos say their new stadium will be ‘privately financed,’ but ‘private’ often still means hundreds of millions in public resources
Rarely are sports stadiums financed entirely with private funds.
