Tldr: I suspect Tesla know what they're doing with the pricing of this thing.
In a big way. They are using data gathered by the self-driving ready hardware to develop the software that will use it.
Thousands of cars out there collecting data is a huge advantage over groups working with a handful of prototypes.
I'm not sure this is true. At least for Google, it seems like the main bottleneck to progress is engineering time to fix the problems that arise. The problem is not a lack of vehicles driving and finding problems.
I say this because Google has made very little effort to expand their fleet of testing vehicles. The last big expansion, from 28 to 48 vehicles, was in Sept. 2015. Since then they've expanded from 48 to 58, but it doesn't seem to be a priority. [1]
[1] https://docs.google.com/spreadsheets/d/1v0BBTDOXvD8JdhrySFy6...
It just isn't reasonable for Google to build and manage a fleet of that size for a development program. It would cost Google half a billion dollars, but for Tesla it's just a bit of cost they roll into the product.