Well, it is silly to subscribe to Office 365 for a single license rental. Microsoft still sells licenses, so that would be the way to go. And in that context, read-only access to those files via Office for iPad is free.
If Microsoft were to *sell* Office for iPad for $90, people would complain that it is too much money... because it doesn't fit in with the price structure of iOS apps.
For my household: 2 notebooks, 1 desktop, 2 iPads, and a Surface 2(Office 2013 preloaded), the subscription model works out pretty good (especially after getting a deal for a 1 yr subscription for $65)
Having said that, I too am greatly against renting software.
I don't need to see it. I can believe it. But what betrays that statement is the chest-thumping over the subscription model. If the average person can get by with the free iOS iWorks, then why all of the bellyaching over the "unfairness" of the Office subscription pricing? The reasonable response should be, "oh well, for those that need Office that's good, but I'm good with the free iWorks!"