I was taking an idea, Cain's I think, and building a smart car, one with a robotic pilot and some related tech.

One of the available autosofts is Performance Profile (Vehicle Type), meaning for a specific vehicle that hasn't been modified too much. Autosofts require an Autosoft Interpretation System, the cost of which is based off a Pilot Rating, the cost of which is in Design Points which is for vehicle manufacture.

So do most vehicles come from the factory with a Robot Pilot option?

you can look at the stats listed in Rigger 3 and see that the answer to that question is no. it's up the gamemaster to determine how much is too much when it comes to vehicle modification and performance profiles, but any GM who makes a performance profile unusable on a vehicle simply because the vehicle has been modified with a drone pilot and an AIS is an idiot.

There should be a cash cost for all of those options, I think, in addition to the DP cost.

Well. I'll admit that in RL terms I don't know how much a robotic pilot differs from a drone pilot, but I wouldn't imagine that it'd be impossible to write a robotic pilot for a vehicle that already exists. I'd abstract from where they convert DPs to for normal pilots and apply that to the robotic pilot modification. IE: You'd be paying a LOT for anything but a rating 1.