When you buy your Microsoft product on a shop you are buying a boxed product.
It's usually a one time buy and a more expensive solution.
When you buy a new computer or server you can buy a pre installed operating system or microsoft office.
This solution is usually very cheap.
But this software can only be used on the installed computer.
If you are buying a computer or notebook and want a Windows operating system the only solution is Microsoft OEM.
Volume licensing is the best solution for 5 or more Microsoft licensing.
There are several licensing solutions like Open Value, Open License or Open Subscription that allow the buy or rental of Microsoft licenses.
365 / online licensing
Online licensing from Microsoft for Office products.