alt Hacker NewsVendors now cannot get X pounds with Y pounds advertising outlay to make Z pounds per unit of wares. To continue making Z money per unit of wares, with previous S pounds price charged to consumers per unit, add significantly more than reduction in Y advertising per unit to S to offset reduced "brand" "awareness".
Brand awareness is a Red Queen’s race. Attention is a finite resource, and ad spend mainly exists to counteract the spend of your competitors.