Businesses such as the Atlantic are not obliged to take advertising from all comers. Showing up with your $50 or whatever does not guarantee you equal time in anybody's magazine. In fact, even if it did it would be ill-advised, if the brands are contradictory; you don't expect to see a Walmart ad in the New Yorker yet I'm sure Walmart can afford to run them there, likewise you don't see Louis Vuitton ads in PC Magazine. Both parties in the advertising relationship are free to choose and refuse each other, like any other contractual arrangement between people or corporations. This isn't a first-amendment issue.