Lack of competition is definitely a problem in the pricing of some things, but I don’t think this is one of them, people just prefer what Microsoft offers and are willing to pay for it.
Google has made some progress here, but doesn't seem interested in a bunch of important spaces (e.g. they have Docs, but don't have anything like Active Directory or Sharepoint that I know of).
Microsoft is also often the default vendor, since virtually every big company has contracts with them for Windows and Office (at least) already.
If a company is winning simply because they’re able to prevent meaningful competition (such as Google buying up default search) that’s a failure of regulators.
If a company is winning because people like their product better and they’ve spent a lot in R&D to make it better so it would cost a lot to catch up to, and it has several competitors who just might not be as good, that’s exactly what you hope for.