Well, technically they are not monopolies.
They are the only leagues that we confer MAJOR-LEAGUE status upon, but I don't see them feeling threatened by little start-up leagues.
There is a barrier to entry - enormous start-up costs. But have the existing major leagues conspired to stop individuals that foolishly want to piss money away on a competing venture ? I don't see obvious evidence of that....
To start up and get a competing league to the point that it is sustainable, you have to do the following:
1. Get some TV partners who are willing to help foot the bill.
2. Get decent players and coaches with name recognition, so that the teams in the new league have some credibility
3. Get access to some decent stadii / arenas for the games.
4. Get the fans to come on board.
Ten AFL teams merged with the NFL (I'm not sure that the Cincinnati Bengals and Miami Dolphins weren't created after the merger was announced). Oakland, KC, San Diego, Denver, Houston, Cincinnati, Miami, Buffalo, and Boston (New England) were non-NFL markets. Only the New York Jets competed head-to-head with the Giants.
Four ABA teams survived to merge: Denver, Indiana, San Antonio were untapped markets. Only the New York Nets competed with the Knicks.
Four WHA teams survived to merge: Quebec, Hartford, Winnepeg, and Edmonton. All were non-NHL markets.
Here's the lesson.... go after those markets where you have an unserved fan base !!!!
Those markets tend to be smaller, but there isn't the withering competition from the big boys, and you can get dates at the local stadium / arena.... the big obstacle then is money to sustain the organizations until there is enough credibility to get a TV contract and achieve some level of profitability.
And still it's HARD... let there be no doubt about that.
if they are not monopolies then why in the 80's they lost the lawsuit to the usfl and the usfl only won 3 dollars? I guess its the so called anti-trust exemption which is fake and part of voodoo economics we have in this country.