Philip Elmer-DeWitt from Fortune Online provides one relevant statistic and one April Fool's joke about the Macintosh. First, the relevant bit, which is of course close to my heart:

According to IDC, Apple’s worldwide market share grew from 2.4% in 2006 to 2.9% in 2007. Piper Jaffray’s chief Apple analyst Gene Munster is conservatively modeling global market share to remain flat this year, but he notes that enterprise sales account for 70% of the worldwide market, a segment Apple is not aggressively targeting. In the consumer market, where Apple does compete, he estimates the Mac’s share is now 10% worldwide and an impressive 21% in the U.S.

Put another way, once we contort the numbers in two ways in Apple's favor (first, by focusing solely on the US market, where Apple's market share is highest for obvious economic reasons, and secondly by completely ignoring a full 70 percent of all PC sales), suddenly, Apple's market share doesn't look so bad. (Actually, there's a third contortion here, as "consumer sales" aren't easy to measure, so this is mostly an educated guess on the part of Munster and IDC.)

These kinds of manipulations may seem unfair and, of course, they sort of are in the sense that statistics can be used to show anything. But let's be honest: Apple mostly targets the consumer market with the Mac. (On the flip side, when Apple targets the business market with the iPhone this year in order to reach its promised 10 million units sold milestone, few Apple fanatics will draw this distinction or have a problem factoring in business sales when they tout that machine's successes. They're cute like that.)

So what does this all mean? In Apple's strongest market by far, and by guessing at what consumer sales are, the Mac gets about 21 percent of the market. Despite the dubiousness of the measurement, I'm willing to accept this as relevant and "true": About 1 out of every 5 PCs sold to consumers (i.e. students and other individuals) are Macs.

Here's the April Fools bit:

Although consumers and investors tend to believe Macs cost 20% to 30% more than comparable PCs, according to Munster, he did some price comparisons and found that on average, the price difference is closer to 16% for desktop machines and 9% for laptops — essentially unchanged from a similar comparison he made two years ago.

This is completely irrelevant if cunningly argued. There's a myth of there that Macs and PCs are comparably priced. But this isn't true. What's true is that "comparable" PCs and Macs are comparably priced. But Apple only sells a few different models. When John Q. Consumer shops for a PC, he's doesn't compare Macs with comparable PCs. He compares Macs and PCs. And what he will find, for example, is that he could buy a low-end Macbook notebook for as low as $1099. Or, he could buy a low-end Dell Inspiron 1525 notebook for just $499, less than half the price of the Mac. Are they comparable? No, not from a specs perspective. But that's not the point, nor is it how people shop. (It's like arguing that BMWs are comparably priced to Fords. Maybe they are, for "comparable" models, if there are such things in that market. I don't know.)

PCs are still less expensive than Macs because there are far more choices in the PC market. One of the choices you get is to buy a less expensive machine with fewer options.

Anyone who believes otherwise is, well, a fool.