Re: you pay 7 bucks for a coffee?
The rest of the staff and entire production floor are running Linux workstations with Open Source office software that costs us 0 to run.
Obvious, you mean that there's zero license costs to run. There are still support costs, energy costs, hardware costs, etc., some of which would be equal and some not so much.
Most every Linux deployment to replace Windows has come with higher initial support costs. The question is whether those costs drop over time. With some forward-thinking design, the answer should undoubtedly be yes, but unfortunately support costs never seem to factor into estimates of TCO until it's too late.