Snow Leopard ships August 28 and, if Gene Munster of Piper Jaffray is correct, it's going to be one hell of a high seller. AppleInsider reports that the Apple analyst believes the new OS will sell 5 million copies during the September quarter. In financial terms, that's $66 million in additional operating revenue for Apple this year.
The $29 cost is listed as one of the primary reasons for the (anticipated) high sales. Munster believes that Apple is keeping prices low as a way to draw customers away from Windows 7. They've gone all out on Snow Leopard in hopes that it will outshine Microsoft's latest offering. Considering the winning streak Apple has been on this year, I'd place good odds on them succeeding too.
Munster's iPhone sales estimates were off by quite a lot, but it was due to underestimation, not the opposite. It's possible that we'll see Snow Leopard sales much higher than even these high expectations. If so, that would mean bad things for Microsoft. They're relying on high Win 7 sales in October to lift them out of their software division's current rut.