Great, then let me buy a specific version as a single purchase.

Would you be fine if that version is affected by botnet in the future, or if the documentation is not updated for newer windows version unless you pay.

And would you be willing to pay $200 one time or $10/month(say assume the average subscription time for users is 2 years), so to recoup the amount they need to increase the cost a lot.

There is a lot of software sold as a single-time purchase for a reasonable price, so it’s certainly possible to make it work.