You're going to over pay but if you're looking for snacks, drinks, reading material, souvenirs or whatever else you might find handy on a flight, this is the place to go. You'll probably pay around $4 for a snack size bag of chips, $3 for candy bars, $4 for a bottle of water... you get the gist. But it's not like you can easily leave and head down to the local drug store.
The good thing is the selection; they've got all of the most common "necessities" and then some. And if you've realized at the last minute that you've forgotten to get a souvenir for someone in particular, chances are pretty good that you can find something here.