I'm just tired. On the last post about having Linux at our work, many people that seems to be an IT worker said there have been several issues with Linux that was not easy to manipulate or control like they do with Windows, but I think they just are lazy to find out ways to provide this support. Because Google forces all their workers to use Linux, and they have pretty much control on their OS as any other Windows system.
Linux is a valid system that can be used for work, just as many other companies do.
So my point is, the excuse of "Linux is not ready for workplaces" could be just a lack of knowledge of the IT team and/or a lack of intention to provide to developers the right tools to work.
I won't comment on point 2 as I think that has been answered suffiently. On the final point Linux support is more expensive. First line Linux support pays better than first line windows support because well. It is still nieche so workers can command better pay.
You will also have to go through your whole application library and make sure it works, if it doesn't can you get it to work or do you have to move applications? That will be expensive and time consuming, more than likely someone does something once a year which is really really important who gets missed and you swapped over 6 months ago and now you have to hack a way for this process to work in 2 weeks to meet the deliverable.
This isn't including training your staff. You have to retrain everyone which is going to be expensive. To be blunt a lot of regular users barely know how Windows works and any change to their way of working is going to be hell. Then you have the cost of retraining the whole IT department which is going to cost more than the regular users.
Sticking with what you know may not be the right thing to do but it usually is the safest option.
Don't get me wrong I would love Linux to take over the office space but I can't see that happeing in the next 20 years. Maybe in a startup it'll work but, moving from something so entrenched in your company is a very big and very scary ask.