So dev costs are $300M. Plus marketing. So it'll be $400M+ for sure.
Just to break even, # copies sold x avg profit per game sold.
$70 US digital sale (Sony gets it all) = around 6M copies. This would be the lowest copies need to break even
(Edit. More than 6M needed as each game costs money to make (dev + marketing)).
But when you factor in sale price, retail copies etc.... if they cant front load sales at full digital price, then the copies needed goes up.
And to make the game even worth making, add profit requirements on top of it which requires more copies.