When Apple first introduced the 12.9" iPad Pro, its larger screen size compared to previous iPads wasn't just a physical difference. The extra inches compared to the earlier iPads' 9.7" screens also pushed the larger tablet into a different Office 365 licensing bracket. Simply put, users needed to purchase an Office 365 subscription to edit documents on the iPad Pro.
We're reminded by analyst Wes Miller that, in being smaller than Microsoft's cutoff of 10.1", the new, smaller iPad Pro is more like its previous generations in that it can edit Office 365 without the need to purchase a subscription.
Office 365 isn't a particularly expensive product, with the Office 365 Personal option, for example, costing "only" $69.99 a year (or $6.99 a month). That's not a huge investment, but it's not peanuts, either.
Of course, when you purchase a Windows machine and Office 365, you get access to the far more robust Office 2016. Arguably, that makes the investment in a subscription a much more economically valuable option for Windows users. In any event, Microsoft's licensing policies makes the smaller iPad Pro a less expensive device for iOS fans, even beyond its lower purchase price, even if it's not nearly as productive a device.