A common misconception in advertising is to think that the outcome is directly proportional to the budget, whereas the same budget is spent on a weak creative; with a strong creative, it turns into investment. It is not the money of advertising that people stop, understand and act on, but the idea.
A good advertising creative does three jobs at the same time: it captures attention, passes the message in seconds, and directs it into a clear action. Without these three, even the highest budget only shows a bad ad to more people.
So the first question to be asked before we start advertising is not 'how much do we spend', but 'what do we say and how do we show it'. If the creative is true, the budget increases; if the creative is wrong, the budget only magnifies the loss.