In general, if you factor in the cost of similar hardware, a windows box isn't much cheaper-sometimes it's actually more expensive. The real problem with pricing is that the lower priced macs use laptop components in order to remain so tiny. These components are simply more expensive. So, there is no budget mac.

However, those imacs come with a VERY nice monitor, and really are well designed. So, while you could pay 699 for a junky PC machine whose fans will burn out within the first year and a half, you could plunk down 1000 for a Mac that probably performs similarly and get a much nicer monitor (assuming that the discount PC even comes with a monitor).

As for percentage of users, those numbers you hear are the numbers of computers sold in a given year. When you factor in the fact that businesses are counted in that number, those numbers are completely irrelevant when it comes to home machines. Many of the machines that are sold as windows machines end up in some closet serving filesystems or running a webserver or something. Certainly not potential candidates for entertainment software regardless if windows remains on the machine or not (and the same is true if it actually sits on an employee's desk)

It would be interesting to know the percentage of Poser sales for Mac/Windows.