The point I was trying to make was, if advertiser's increased profits were less than the expense of advertising (e.g., a company spends $20 on advertising, but

The point I was trying to make was, if advertiser's increased profits were less than the expense of advertising (e.g., a company spends $20 on advertising, but profits grow $10), then they the company would not advertise again, since that would be as effective as burning money in a pit.