Those who can't affort windows, let them try alternative. No one is forcing people here to pick windows and moreover, for those on a budget, linux suites well for them.
MS sells millions of licenses for each of it's operating systems and that is their market.
And for those in places like, say india, there are versions like Vista Home basic that is avaialble for some 2.5k and Home premium for some 4k.
I don't think that this is a heavy amount to pay for an OS. You might feel that it just an OS, but ask someone working in OS design teams how much effort and headaches they take. Supporting millions of devices is not an easy task and naturally, we are the one that have to pay the price.