It's $120-160 and you use it every time you turn your computer on. I really don't see what the big deal is.
Its no different to buying games, you buy a game per pc unless you don't plan on going online or ever connecting the internet to your pc.
Well, it is, Your computer will still run if you don't buy Half life II, I would liken M$ along the lines of the Oil Companies... Yes we don't HAVE to have oil to survive, but if we want to go anywhere or do anything with a mechanical vehicle, then welcome to fossil-fuels. Same concept with OS producers... Yes, you can live with out it, but if you want to ever use your computer for more than a desk weight... then you get to support the monster.