TranMingTrong, when there are major changes from one version to another (example: 3.xx to 4.0 = upgrade), Stardock charges. Between 3 and 4, no charge for updates.
MS encouraged people to go to W10 from W7 and on certain machines from W10 to W11 as a migration ploy. But, if you buy a new machine, you pay for the new OS.
There's no secret to any of this, it's been written about many times in forums, yet people continue to misunderstand real world stuff: Salaries have to be paid. People don't work for free. Developing software to meet changing operating systems and to offer new and different features costs time and therefore, money. Therefore, when there's major change, there's a charge.