Is the bus not the same as the magazine, where you can go "oh look an advert, I'll just ignore that and get back to my content"?
I'm not sure about the value of magazine adverts, I've never worked in print advertising,MIT even at a few dollars that would mean you have to pay double. If they raised prices to do that, the higher price could/would drive some people away, meaning you'd then have to pay more to cover those lost sales..