There aren't really any licensing fees for Android Auto. Apple charged a few dozen dollars for the right to produce a car with the integration, rather than a license as such. There's integration costs and hardware, so it's not free, but generally it's cheaper than the alternative.
Android automotive, the system GM is discussing here, is more expensive in every way than Android Auto. The reason they're switching is that Android Auto/carplay don't give GM enough additional monetization options for customers.
Is it possible Apple/Google initially charged a nominal fee when the technology was brand new, and now that it has widespread acceptance and is mandatory for many car purchasers, they turned the screws and are now charging an exorbitant price?
It's possible, but it wouldn't lead to this kind of action. Automakers already have a way to deal with expensive features that are critical to a large segment of the customer base. They limit it to higher trims or select models, depending on the cost constraints. That's what GM does with ADAS for example.
They're eliminating phone projection entirely here, which means they think the feature is incompatible with their business model.
What is the economic incentive for Google and Apple not to do this? They've convinced much of the public that it's a necessary feature (moreso than SiriumXM, for example, which also starts free then costs a lot), and better than what the manufacturers can develop internally, so why allow the manufacturers to integrate it for such a low price?
Android automotive, the system GM is discussing here, is more expensive in every way than Android Auto. The reason they're switching is that Android Auto/carplay don't give GM enough additional monetization options for customers.