Airport stores don't have a reputation as savvy places to purchase stuff, due to high markups. But that's not necessarily true, says Baskas. Some municipalities (like Portland, Austin, Atlanta and Pittsburgh) have explicit rules that forbid on-site shops to charge more for the same goods than at nonairport locations. (Hint: Look for a posted sign.) Also, find out about the sales tax where you're changing planes. Oregon, for instance, has no sales tax. That means you could save up to 12 percent on your purchases, depending on the sales tax in your home state.