I don't mind them charging for a service that has ongoing costs and I don't mind them making a profit doing so.
But 70% profit?
That is basically extortion, or as the economists would say: Rent seeking.
Once you have purchased a car, they are a sole-source provider for such services. So, a monopoly.
Since we have decided monopolies are AOK in this country, they just charge whatever they can get away with and that is that.
Let's see some real competition required in this space - such systems are built to a standard and you have a choice of at least 5 or so subscription services that will do the same job, regardless of the make, model, or age of your vehicle. Or if that kind of competition isn't happening then regulate the service like any other utility monopoly - including a cap on profits.
5-10-15% or even, at the outside, 20% profit in an industry like this would be somewhat reasonable, and more than enough "reward" for investors and company owners.
70% is nothing short of highway robbery.