People are already spending nearly $1,000 for something that still isn't a full computer. Have you seen the full price of an iPhone 6s Plus?I understand all of that, but I think that a lot of less "techie" people, so to speak, will be among those asking, "why should I pay $1000 for something that still isn't a full computer?"
For many people, the smartphone has become their primary personal computer. And those people use those smartphones as laptop replacements for most of their personal use cases despite the fact that smartphones generally don't have file managers (although there are some optional file managers for Android). For them, the main limitation of their smartphone is the size of the screen. The iPad Pro gives them the iOS environment that they are accustomed to plus a massive screen. If recent history is any indicator, the current iPad Pro will drop in price in the next year or two, which will make it more affordable to more people.