Advertising is not zero sum because a company can choose to keep money rather than pay for a marginal ad, which may be more profitable. Microeconomics indicates

Advertising is not zero sum because a company can choose to keep money rather than pay for a marginal ad, which may be more profitable. Microeconomics indicates that increased per-unit costs to suppliers (advertisers) decreases quantity sold. I'm not sure I understand your argument for why this would not apply. Although, I will note that giving advertisers disinformation resulting from adnauseam loads is probably a much more significant effect than the cost of serving additional bytes.