Although it will be impossible to substantiate, I would expect that Tesla's AP at this point has saved more lives than it has cost.
It has certainly prevented a number of accidents, of which some could have caused fatalities.
Although the Model S is a very safe car, even the driver who was tragically killed while using the AP could in principle have had his life saved by it on a previous occasion, e.g. the one he got so much attention for when the AP saved him from that truck doing a dangerous lane change. Being a former navy SEAL he was used to familiarize himself with equipment on which his life would depend (e.g. diving and parachuting equipment), so I could imagine how he saw how the AP had previously saved him, and then put too much faith into its capability.
We will never know, but when used correctly, I feel confident that the AP actually offers some protection against human stupidity and I would not be surprised if it already now has had a net benefit.