While 65m for ant-man is true from an economic standpoint this new guy has a point.
You have 100m dollars to spend on a movie, you could make Ant-Man or Minions. While both will make a profit, itd be much better to invest that 100m in Minions because it will yield the higher return. (Just an example I know marvel can't make Minions)
However, Marvel budgets usually range on the 200m end, if Ant-Man is only on the 100m end budget wise, it could prove to be a much better investment than say The Dark World because it only has to make half as much money to wield a profit.
If it gets 400-500m WW itd be a bigger success than Dark World, and possibly Winter Soldier. Biggest difference here though is Winter Soldier and The Dark World will both increase awareness (and profit) for future crossovers like Civil War and The Avengers, and merchandising is going to be much more popular for them than Ant-Man.
Tl;dr Don't go into Opportunity Cost when on a box office forum because the discussion would only be long and painstaking for a single movie.