Doesn't matter. The cost of the OSX upgrade above neglects to mention that it requires upgrading to the previous version first: If you are on Leopard, then you pay $30 for Leopard -> Snow Leopard, then another $30 for Snow Leopard -> Lion. If you want to jump straight up, then you usually pay $100+ for a 'box set'/
Microsoft are not nearly as secretive as Apple wrt their OS updates, and you usually have at least a year's notice, plus OEM free upgrade programs if you buy a PC with Windows pre-loaded within a certain amount of time before the launch of the new OS. Of course, you can still get screwed over by unscrupulous salespeople if you are relatively ignorant, which can't really happen in the Apple scenario above, since you need each upgrade.