Over at smartertravel.com they tell us that "Airlines,' 'advertising,' and 'honesty' should never be used in the same sentence. The airlines' promotion of their cushy first-class seats is clearly a case of trickle-down advertising, meant to suggest that comparable comfort and tranquillity may be enjoyed in other classes of service as well. And no one who has endured a coach-class seat on a cross-country flight would consider that a truthful honest claim."
Airlines are no different from almost every other advertiser. When did you last see a car ad that showed anything less than the top of the range car, as revealed by the small print at the bottom of the add, which costs way more than the basic model.