Who do you know can afford to pay $285 per seat? Certainly not the wellfare queens in DC.
The stadium probably can't seat more than 50k, so estimating 35 thousand attendance per game (Highly unlikely), you could never recover 10 million per game.
And you really expect DC to recover 5-700 million dollars in taxes down the drain ??? What's good for Major League Baseball is good for DC Gov. . .
In other words. . . .you want to rob us, MLB, we'll steal it right back