You're treading a fine line here - there's no need for posts like this.
So you don't see the added value of a Mac? OK - so if you have trouble setting up your HP printer, can you call Dell to help you set it up? If you can't get your phone to sync, can you take it to a Lenovo store to have them set it up for you - free of charge? Also, when it goes wrong, can you walk into an Acer store and have them repair it on-site, often while you wait? Yes I know Dell do on-site repairs, however you have to pay a premium for that service. I'm sure HP will let you take your HP Laptop and your Sky router into one of their stores and will help you setup your wireless for free, too. Those people working in stores and support cost money too.
As for off the shelf components, beyond the CPU, GPU, HDD and AirPort card - nothing is off the shelf. It's all custom designed and engineered with an amazing amount of precision - take one look at this, and tell me, seriously, that it's any competition for any "build your own" box - http://cdn.mactrast....ac-teardown.jpg - engineering to those levels costs money.
Then there's the little things, such as the cooling system, which has fans with variable blade gaps to reduce noise levels, and has custom designed heatsinks to dissipate heat using the Aluminium casing. And the SSD - is now PCI-e. If you order a fusion drive for £160 - you get a HDD and a 128GB SSD. Now, I tried finding a 128GB PCI-e SSD with the same performance for £160 - and failed. Best you can get in that range is SATA.
And as for the LCD - you can't compare the iMac to any cheap 27" display. If you want to do a fair comparison, then you'll have to compare it to an LG 27EA83 - which uses the exact same panel as the iMac. Or the Dell u2713 which uses the same panel as the previous gen iMacs. You'll note that these will set you back £400 (Dell) and £600 (LG) plus.
And I haven't even started on Software. Want disk encryption? You're going to have to go for Windows 8 Pro. Filevault is included with OS X. Want Visual Studio - prepare to give over another £500. XCode is free with every Mac. Also - how much was a Windows 7 to Windows 8 upgrade? Lion -> Mountain Lion was £15. Soon adds up.
I don't want sound like I hate macs... but seriously, if all that stuff is not made by the owner of a PC... then yeah, they deserve to be charged as hell for that. (PC owner ranging from the very first computers with 386 processors)