MS licensing vs.OSS
The cost of licence managing / accounting is a huge part of the cost of licensing for larger organisations. The overhead in dedicated procurement teams / asset management is significant. Then you pay for consultancy / outsourced expertise to sort out problems with your asset management / licensing management software. That's on top of costs for patch management / badly written third party software
That's a chunk: then there's using a Miicosoft / Oracle trusted partner for large scale licence provisioning and deployment and "independent" auditing.
Then there's the cost of upgrades and other products from the same vendor which predicate existing infrastructure: Windows Server + AD + Exchange + Office + Sharepoint + Visio ...
Back end: Linux every time.
LibreOffice - as functional as any MS product - and more backward compatible with the older formats. If you're running your business on Excel - GNUmeric will do everything related if it's arithmetic. Bigger data - you should be using R. Databases - MariaDB / Postgresql ...
If you build local custom macros for busines procesess without version control / central scrutiny / auditing - you deserve to fail If you use Access databases for mission critical data, you've already failed and your business is dead: you don't realise it because the pacemaker and life support are still running.