Quick Google search tells me there are currently 65 million GM vehicles on the roads in US. Let's say that can add 25 million new ones till 2030 which sounds very optimistic for them. To have their forecast of the subscription revenue materialize they would need to charge 1000$ per car per year or about 80$/month. That seems crazy to me. People might be coming to terms with subscription but 80$/month is an expensive…
So no, they're right in line with right how they want to gouge customers.