Demand, in economics is represented as a graph of purchases versus price. By definition, a change in price does not change demand; it simply represents a different point on the demand curve.<p>What <i>does</i> change demand is customer perception that they're being ripped off. A $515 ticket and a $500 ticket are fairly close on the demand curve and probably don't represent a huge difference in sales. A $500 ticket plus a $15 checked bag fee is perceived by the customer as an attempt to conceal the true cost of the ticket.