Here's the problem with all of those examples (save for the best buy one), you buy your car. You pay your finance for it, you can go ahead and disable that check engine light at the 30,000 because yeah thats not right for them to do. But its your car. If you do skip out on that and fix it, it doesn't cost them anything. If you buy your cheap cpu and decide to overclock it, it doesn't cost the manufacturer anything.
When you take a device that is being provided service, service that is not free to run, then it becomes something else. I agree, we pay for our "unlimited bandwidth" and hell yeah we should be able to tether whether it be USB or wifi is irrelevant. But the fact of the matter is you are paying for a service that you have no say in how it goes. The only say you have is yes or no. When you start breaching your contract you are riding a line of when/will I get caught.