Don't believe the MS bull... This isn't cheaper at ALL. Remember with the subscription model you HAVE to maintain an internet connection, so add that price on as well, along with the price of all the hardware to actually have an internet connection.
Then there is the utter lack of trust such a subscription model will have - if I have to log in to MS to type a letter, what guarantee do I have that MS isn't reading and indexing every document I have? What if I need to write a letter on my laptop, on the move with no net access?
If the software can at any stage be operated offline, then you know for sure that crackers are gonna have at it in no time.
So, if it doesn't prevent piracy, and as such generate more sales, why would MS price it cheaper? Oh I know! To get you hooked then drive the prices up mercilessly!
Don't like paying a few hundred for a copy of office? Try paying a few hundred a year, or a quarter...