I mean, what're they gonna do to stop you, really? If they're dicks about it you can easily go in, see what you're interested in, pop over to the nearby coffee shop and look up prices, then go back.
I do understand their frustration, mind you. People think they can walk into a store and expect to get online prices, they're completely ignoring that this place has to pay rent and employees, as well as that they are providing you a valuable service of seeing, touching, and even TRYING the game(s) before making a purchase.
Buying a game in a store is not equal to buying a game online, period.