They probably do quite well. Comparatively well-heeled crowd often with long periods of time on their hands. Even if the sales aren't great it's a good way to build name recognition among a desirable customer base.
In addition to buy toiletries, books, etc. I can recall buying a flashlight, a Tumi wallet and a computer bag. The computer bag was used to replace the one I had that was falling apart. I've also used the airside stores to look at items and then later buy them when I got home. I've also been tempted many times by the watch dealers at airports particularly during a 10 hour layover in Munich.