It is much more economical to invest in local open source people to take care of the tech need than big corp. Big corp are notorious unreliable over long period of time, their incentives are NOT aligned with the customers, only with profit and/or 3 letter agencies.
Most people don’t know much about the OS or Office, so you have to train them anyway for the companies use cases and non standard programs.
MS just seems convenient, but isn’t. In large companies every update brings problems.
Things like Teams change the UI quite often which leads to support questions.
So for me the training costs don’t differ that much.