Just to clarify, in case someone not at all familiar with Zorin reads this thread:
(1) Zorin OS has four editions -- Ultimate/Pro, Core, Lite and Education. Core, Lite and Education are free; Ultimate/Pro costs $39 USD.
(2) Core includes a selection of installed apps similar to Ubuntu and most other distros, specifically including (in light of your comment) LibreOffice. Core is more than adequate for most users.
(3) Ultimate/Pro adds (a) the convenience of a boatload of pre-installed software, (b) extended desktop theming, and (c) installation support. All of the pre-installed software is available in the repository; the difference is that Core users have to install the software and Ultimate/Pro users do not.
I would encourage you to take a look at the download page, and specifically this chart at the bottom of the page:
To put this in perspective, the Ultimate/Pro ISO is about 4.2GB (Zorin OS 15), while the Core ISO is 1.6GB. With Ultimate/Pro, users are paying for the convenience of pre-installed software, extended desktop theming, and installation support. That's it.
To look at this from a different direction, Artyom Zorin said in a Forbes interview a few years ago that Ultimate/Pro edition customers have made it possible for Zorin OS to thrive and remain a full-time project. That's worth something, it seems to me, particularly for those of us who wish to support the Linux communities from which we benefit.