Originally Posted by metaphysician
I think there's an easier explanation: the 300M number includes their marketing budget, which is otherwise always separate from the production budget anyway.
Avengers marketing was in the realm of $150 M. That figure definitely doesn't count marketing.
I believe it was the Wall Street Journal that said the actuals for Avengers were $300 M production/ $175 M advertising. This film cost WAY more than $220 M to make, and way more than $80 M to market.