You don't pay more to apple, you pay more cause of your tax laws.
More expensive because of tax and...
US: 27" iMac (3.2GHz stock): $1,999.00 excluding tax.
UK: 27" iMac (3.2GHz stock): $2,273.32 excluding tax.
Difference, before tax: $274.32 more in the UK.
Source: store.apple.com/uk, store.apple.com/us, xe.com/ucc (1 GBP = 1.60545 USD, Mid-market rates: 2012-12-07 03:23 UTC)