In the future just point to Superman Returns when other claims it just needs to make as much as its budget to get a sequel. Superman Returns had $270 million budget, made $391 worldwide. Never got a sequel.
Yeah, although the $270 million is inflated with the costs of the previous cancelled Superman projects. Then there's John Carter
, which did $282.7 million on a $250 million production budget - a disaster that Disney lost a lot of money on, which is a pity because I personally enjoyed it and would have liked to see a sequel.