@Anton Nothing against your model of different CPU levels, I completely understand, that it is expensive to host such a project and at some point you event want to make some profit with your hard work. Also, I'm not going to rant about the fact that other people who invest more money have an advantage in this game.
However defending that system in the way you do is - please forgive my harsh words - either plain stupid or deceitful.
In your article and your recent answer you basically want to make us to believe that the guy with the Ferrari has no advantage over your racing kart because he might not be able to drive. This is just ridiculous. Given equal driving skill (which you have to assume in the first place) he definitely has an advantage. Nothing to discuss about that.
Secondly, your claim that having a flat subscription fee will not work, because people would abuse the system is nonsense as well, because with the current model, somebody could still have multiple accounts giving them an edge over people who might run on 300 CPU but only one account. The problem is exactly the same, it just manifests at a different level.
Again, I am fairly okay with your current payment model, I'm just majorly annoyed how you try to justify it with flimsy excuses. It would be no problem to introduce even CPU levels - it might just either hurt your pocket and/or spoil the fun for many players because the amount of CPU credits is not sufficient enough.
Bottom line: Please - just stick to the facts, that will suit your credibility far more than what you are currently doing...