I think there is a correlation, but not a causal connection. I would argue that, to the extent the glossy ads are effective in creating brand panache that exceeds the quality of the garment (Armani being the best example), then it only makes sense for the manufacturer to water down quality. Until the ads are effective in making the brand conscious consumer want to purchase that brand, I think that the marketing will merely cut into initial margins.
the overall revenue generated is proportianal to marketing spending. if the margin is huge, and the marketing can get people to buy the product, then a lot of money will be spent on marketing. the high margin suggests low value, but that isn't always the case.