If you are speaking about "people", they are not going to pay 10$ for MS Word also, just because most of them used to have it illegally installed on their pc.It's all about branding. So many people say to me "why isn't word on iPad?" And I always respond with "Get Pages, it's similar and a great app made by Apple." And the usual response is "$10!??!??!? That's way to expensive! Stupid Apple."
People woul pay $10 for word because of the familiarity of it from windows.
A true pro user who need a text editor with some capability (and maybe a good compatibility with the desktop version) can judge by himself what is the best app in the Store, Pages, word or whatever, and pay for it.