Frozen will not need to make $600 million to break even. A film's marketing budget is not associated with just the film's budget, as Disney has a marketing department that markets nearly all of their different products. The marketing budget for Frozen would be a part of the marketing department's budget, rather than the budget for the film.
The marketing for Frozen markets much more than the movie. It markets toys, video games, clothing, theme parks (to an extent), and much more. To only count a film's gross verses a marketing budget is silly when there are so many more factors that go into play.
Obviously, the more money Frozen makes, the happier Disney will be. However, Disney spent a similar amount of money, in both the film's budget and marketing expenses, on similarly budgeted movies that ultimately made less money (Chicken Little, Bolt, Tangled, Wreck it Ralph, etc).
The truth is that anything over $300 million would be OK, $500 million will put it among the ranks of Disney's best animated movies. Things are more realistic than they may seem and movies studios make much more money from movies than it may seem like. Frozen is a hit.
