Perhaps it's time for you to become familiar with the terms of the Mozilla Public License, under which Libre Office is released. There is no requirement for monetary compensation.
They chose -- explicitly, voluntarily, knowingly -- to give the thing away for free. That's their right for their own creation. Your preferences don't supersede theirs.
By profiting off their work and not supporting them you are making your own choice. It says nothing about the authors' preference.