The question is: "are staffers $14 / mo more productive with it, than the free version?"
The answer may also boil down to satisfaction, support calls, other things, aka 'total cost of ownership' as well.
Not 'But it costs $X million!'.
Companies will spend a fortune giving staff the right monitor, or chair, but literally don't think they're smart enough to know the dam tool they use all day?
Let them pick their chat software, like they pick their monitors.