I assume that it was pressure from many users that forced them to bring out the mod. which enables older versions of Word to read .docx files.
I suspect you'll find that they had that they had the Compatability Pack available to everyone from day one. Reason being they have large customers where immediate overnight roll-outs from one version to another is not possible. But it was definitely available for everyone to download free from their site from day one.
On your other points about enforcement and profits, it's been a long week and I'm too tired to argue. But software development is an industry with large overheads, over and on top of normal day-to-day business overheads. I think it is only right that any software development company (Microsoft or otherwise) should be entitled to charge what they like. If people don't like it, there are pleanty of open-source alternatives out there these days.
The Microsoft OEM license is sold at a cheaper price because of its restricted licenses.