Jimbo,
I think you are going a bit over the top, they must cover the cost of having the store open, that is why stuff online is usually cheap. I'll admit the service in PC World is varied, some people think it's great, and it's definately improving.
Behemoth said it, very low margin, a lot of stores rely on these services among others. You pay for the store as a whole, you pay for the service 'package'.
You have to look at the whole system, not just sections. I dislike Apple, but i also congratulate them for their success and the innovation in their products.
The tech guys are very skilled - it's a bit like being a fireman, you're saving cats stuck in trees for 6 days of the week but on day 7, the hospital sets on fire. You're not paid for the easy stuff, you're paid for the overall knowledge/skills you have, whether it's easy or hard.
As usual, it's managements fault when it comes to cost.