Re: US State Department employees ask Hillary clinton for Firefox - Video
I'm sure if they were to do a feasibility analysis, it would be lesser money to include FF in the overall portfolio - users who switch to FF and take care of their own issues because now they're able to... won't be calling tech support as often for minor things. So support cost will actually decrease even if they're going to be supporting two browsers.
I usually don't like Hillary's answers but I liked her point about not being productive with tools that are intended to make you productive.