I very much doubt the small bump in sales of Coke after a major ad campaign actually pays for the campaign. That's not the point.
Lets suppose CocaCola stopped advertising completely. No TV adds, no product placement, no billboards, nothing, but Pepsi and the other soft drinks companies kept up their rate of advertising or even increased it to fill the gap. The only time anyone ever saw the name Coke would be when they saw it on a shelf. It might take a while, but the outcome would be inevitable.
Lets suppose CocaCola stopped advertising completely. No TV adds, no product placement, no billboards, nothing, but Pepsi and the other soft drinks companies kept up their rate of advertising or even increased it to fill the gap. The only time anyone ever saw the name Coke would be when they saw it on a shelf. It might take a while, but the outcome would be inevitable.