It's actually not zero-sum unless their marketing is misleading customers into buying products they actually would want less given perfect information. If their marketing introduces new customers who prefer their product, then it's positive sum. Even if those customers are spending money on this instead of something else, they are spending it on this because they derive more utility (of some type) and therefore there's more economic value. Economists don't consider marketing zero-sum - read the article you linked more closely.