When I bought my MacBook Pro last summer, just after its refresh, it was feature and cost competitive with Windows laptops of like design. The "Apple Tax" was at most a 15%. When the Mac Pro launched, it was hailed as being less expensive, in absolute dollars, than any equivalent Dell offering.
In the eight or so months since release, the current MBP has had minimal configuration and price changes (a CPU boost recently?). In contrast, PC laptops of like design have introduced current hardware options and dropped price a bit. So now the MBP is looking overpriced and / or outdated.
My estimate, especially with the Intel-changeover, is that Apple releases refreshed designs about every year or so that are feature-for-feature price competitive with competing, mainstream Wintel computers.
However, Apple keeps their hardware configurations and prices (almost) fixed until the next refresh, and their pricing becomes less favorable -- even to Mac fans.
Why would Apple do this? Increased profits and improved customer service, I expect. Longer-term offerings of the same hardware will increase their order sizes from suppliers providing cheaper prices to Apple. And ordering the same parts as their prices fall also gives Apple cheaper costs. The result is that Apple has better profits over the lifetime of a given product.
It also plays towards Apple's proposition of simplicity -- in buying as well as using their hardware. A simplified product line has been a hallmark for years: fewer options improves the shopping experience by not overwhelming the customer with too many (redundant) options. And by keeping product lines feature-fixed for longer periods it also subtly reduces buyer confusion. There's less of the "if I wait for two weeks, a new option will be out" mania. It supports the Mac concept that hardware has a longer life -- people see their Apple hardware made upgraded and made obsolete less frequently. It may be a false perception, based on actual hardware options, but Apple is about perception and emotion along with actual hardware and software.
For most people, I think this is a non-issue. The typical Mac buyer is a loyalist and is buying a Mac. They're not thinking they'll switch back to Windows simply because the hardware 30% cheaper at the moment. They need to run OS X: cheap PC hardware doesn't matter since it doesn't run Apple software.
And the enthusiasts know that Apple will eventually refresh their hardware options, and again be (reasonably) competitive with the current Wintel offerings. And they'll wait to buy if they're too far out on the refresh timeline (like everyone around here is doing, waiting anxiously on a new MBP.)
TV and iPod Touch. 
