In a statement today, team president John Schuerholz said that Turner needs “hundreds of millions of dollars of upgrades” and that the massive investment “would not do anything to improve access or the fan experience.” (Which is a bizarre thing to say, because Schuerholz later identifies new seating and lighting as the two major renovations Turner Field requires—and wouldn't replacing worn-out cushins and shitty lights actually improve the ”fan experience”?)
Turner Field is not owned by the team. After serving as Atlanta's Olympic stadium in 1996, it was converted into a baseball field and slapped with a 20-year lease. Rather than extending the lease, the Braves decided to move.
The new stadium will be built at the intersection of I-75 and 285, closer to the town of Marietta than Atlanta. Taxpayers will be responsible for $450 million in financing. The Braves are only on the hook for $200 million. The team plans on cutting seating at the new ballpark by 10,000—to 41,000 people—creating a more intimate (and expensive!) setting. There is little to no mass transportation options currently near the site. But a lot of their ticket holders are, which is a pretty good indicator why the team was eager to move.