Not really
They have to have security processes in place anyway to integrate things like Spotify slacker etc so they can piggyback off of that as well and you’re right nothing is ever free but you’re speculating wildly on cost with nothing to back it up. It’s far more likely that this was a mutually beneficial arrangement where Vector Unit got some publicity to spike iOS and Android installs of the game where they make their bread and butter with micro transactions. And I don’t get where you think all the support and systems is needed the model 3 runs Linux and the apis are pretty well trodden at this point the extent of support would be opening internal driver api docs which would also come with standard NDA agreements. MAYBE Tesla is on the hook for some final qa but that would hardly be a resource that’s even 100% committed as it is on the software side given the issues everyone here is winging about
I genuinely hope they are able to provide access to APIs to 3rd Parties with proper security without much overhead. I can think of lot things 3rd Parties could do, like HUD device that shows lot of Data from main screen behind steering which can communicate via Wifi-Direct, or via OBD(however unusual it may be).
Potentially physical controls who would like to have, like example climate control, mirror controls, source/mode controls, drive modes etc.
Tesla could potentially benefit licensing these accessories (Like Apple does).