There's no reason Microsoft has for raising the cost of Windows 7 above that of Windows Vista. It's been 23 years since their profits took a plunge, but even then they still turned a profit despite the recession this latest quarter. And also despite the poor rate of Windows Vista adoption and despite the ongoing huge warranty costs of their Xbox 360 platform.
http://money.cnn.com/2009/04/23/technology/microsoft_earnings/index.htm?postversion=2009042316
Ars Technica has this interesting article about subscription based pricing. I'm not a fan of paying annually just for the privilege of use, but if done right it could save users money in the long run.
Link
Along those thoughts, there is always a Technet Subscription. While the EULA disallows Operating System downloads to be used in a production environment, for profit, and they obviously can't be sold, the Technet Subscription route seems to have some good advantages. The key is good for up to 10 installs, so if you frequently build then rebuild systems it'll last a good while without requiring phone re-activation hassles. If a new OS comes out then you don't have to buy it all over again, just shelve the old one and upgrade at no cost. Of course $350 a year is still a tad much, but knock that down some and it starts becoming quite reasonable as opposed to paying $150 for a one-time use OEM copy of Vista Business that is tied to the motherboard.
I wrote that article.
