I think it's far more likely that this API is intended to encourage fleet deployments of Teslas and value add from third party apps, rather than for the API fees themselves to be a profit center. That seems far fetched, and I have trouble seeing how that could discourage someone from buying a Tesla anyway, since you can simply choose not to use these features like the vast majority of owners today.

There are real costs to Tesla to run this API, likely primarily the cell bandwidth, so it makes sense to pass those costs on to users instead of subsiding them, which would likely lead to inefficient use of the API or even abuse.