During the first quarter of 2008, Macs were the highest selling brand of computer for performance, which means a computer priced above $1000 at 66%. This includes laptops over that price-point.
Now, this statistic is limited to in-store sales, which includes Apple Stores along with big-box chains like Best Buy, Fry's, and Circuit City.
As for desktops sold in-store, Apple has a 70% market share.
While in-store sales are a small fraction of total computer sales, with most being ordered online, it represents some pretty impressive growth for Apple.
This is what happens when you make fancy stores that sell computers over $1000. You end up selling the more of these than anyone else in store.
Most people that are spending a few thousand on computers (save those getting a server) are building them anyway. You can't really build a mac unless it's a hackintosh.. You can barely even upgrade your own Mac unless Steve says it's OK lol.