Apple's exchange-rate math has ruffled the feathers of some British Mac fans who are taking umbrage at the cost of Snow Leopard in the UK.

The retail price for Snow Leopard here in the Colonies is $29. At today's exchange rate that's a little less than £18. Figure in a 15 percent value-added tax, and £21 might be a reasonably equivalent price across the pond. But the single-user retail version of Snow Leopard in the UK is actually £25.

That's £4 more than our back-of-the-envelope exchange, or about $6.50 American, a 22 percent mark-up.

As you might expect, some users on Macworld UK's web site were not thrilled with the mark-up. As one user wrote: "Why does the UK Mac customer always get ripped off by Apple? I know that £25 is cheap for an operating system (albeit a minor upgrade) but you can't help but be annoyed by the much cheaper U.S. version."

Apparently many people had expected Snow Leopard to be priced at under £20 by Apple UK.

But as Lexton Snol of PC Advisor, the British equivalent of America's PC World, pointed out, Apple is not alone in pricing items higher in the UK than in the US. The Windows 7 Family Pack, available for $150 in the US, is priced at £150 ($245) in the UK, a mind-boggling 63 percent difference.