I’m informed that the MacBook Air’s solid-state drive option fits the SAUK model precisely, with no rounding: 110% of (117.5% of (US$3098 in UKP ~= £1569)) = £2028. And Apple doesn’t always round upwards, it seems: the US$99 external SuperDrive comes out at £65.33 before adjustment, and is apparently being sold at £65 rather than £69. What charity.

Reaching back to my mostly forgotten maths classes, you can simplify the calculation to a standard Apple British Coefficient of 1.2925, for those who don’t get to buy ex-VAT (or, more likely these days, on a weekend in NYC).

The Apple Store numbers are somewhat deceiving, because US prices exclude state sales tax, which is paid by most buyers, while UK prices include VAT. But the standard rule of thumb for working out how much extra Apple screws out of British customers is as follows:

Convert the US price, add VAT, stick 10% on top for shits and giggles, then round up to the nearest £49 or £99.*

The MacBook Air fits this, as did the iPhone (figures rounded to nearest UKP):

Rounded up to nearest £99, you get £1199. Voilà.

* Unless it’s under £100, where you round to the nearest £5 or £9. Leopard’s $129 became (£65 + VAT) + 10% = £84, rounded up to £85.