I can say as a former Apple Retail employee, A LOT. Sure there were a lot of customers that sort of knew exactly what they wanted walking in, but those are the same kind of customers who are more inclined to order online. The value-add for those customers is NOT hovering around you, helping get your product quickly and easily, sometimes helping confirm your research/decision (adding to buyer confidence), answering lingering questions or giving first-hand recommendations on things like accessories. And after all that, you'll then recommend going to the Apple Store to your grandma over ordering online or Best Buy.
I don't think most people posting in this forum would understand, but there were tons and tons of people coming into the stores that are intimidated by technology. The warm, friendly, helpful retail staff really helped make the difference, especially with Mac and iPad. Also, a lot of people buy iPhones in Apple Stores rather than carrier stores because Apple has a reputation of having friendlier staff and
Good face-to-face experience with staff also converts not just into immediate sales, but future sales as well. I couldn't count the number of times I had a customer come in ready to spend a ton of money on a top-of-the-line system, but after a brief discussion about their usage I ended up recommending a less expensive model (you don't need a $2500 computer to check facebook and organize your iPhoto). Customers tend to appreciate that honesty, and then not only return to that store for future purchases, but recommend it to friends.
Apple does indeed pay really well compared to other stores in the Mall, but those other stores are generally selling things like clothes, shoes, stationary, books. Selling computers definitely requires more technical knowledge, application knowledge, the ability to relate technical concepts to less tech-savvy people, and at Apple specifically requires refined customer service skills. And the stakes are much higher -- if someone decides to buy their jeans at a different retailer, your jeans store is out $50. If someone decides to buy their computer at the Microsoft Store (who have been actively poaching Apple Retail employees), Apple's out $1500+. It's better to compare to a car dealership or high-end jewelry store than just "retail" in general.