more to the point, it DOES affect things on a global scale. if a country's people are developing mental illnesses like eating disorders because of the unrealistic expectations they feel are being put on them by the media, then the economy suffers. so even if you DO feel that you have to look at this as an economic issue, then it's still relevant.
i have no doubt that the media plays a significant role in the high rates of anorexia and depression in western society, and it is certainly something that needs looking at. people discount the issue because it is only one factor out of many, but that's no reason to ignore it. depsite how much one tries to be indifferent towards the skinny models in these magazines, it is difficult.
furthermore, the magazines add to society's problems by creating a false idea that all people should be living in luxury and that everyone can afford to be. read Vogue, where page after page the reader is bombarded with ads for jewelry (1000's of dollars), makeup (not TOO expensive, but as they say, you need foundation, moisturiser, lip balm, lipstick, nail varnish, shampoo, conditioner, mascara, eyeliner, eyeshadow, blush, fake tan, not to mention countless hair-removal and exfoliation products -- in a year, this can contribute to a HUGE sum of money spent on useless stuff), luxury holidays, concerts, and, of course, the next issue of the $9.00 magazine, made of beautiful shiny paper, for which no guarantee plantation forests have been used.
the difficulty here is that the people have a right to produce these magazines, and if this is what society wants, who's right is it to take them away? so instead of taking away the magazines, we need to address the global issue of insecurity, which we so naively feed with material goods. we need to ask ourselves, "why do i constantly feel the need to have more, to be thinner, to envy others and the spend more, more, more?"
it is a very complex issue and certainly needs more thought from perspectives of politics, social justice, psychology etc.