The Gemini results when I searched for this cited this Reddit post [1] which cites this Reddit post [2], which conveniently gives your $2/mile answer.

Anyway, digging into the Reddit posts which gave your lower-bound number, the reasoning seems very suspect. In particular, the biggest methodological problem is that they use retail price numbers when Waymo is almost certainly getting wholesale prices. So it assumes $110K ($70K for a Jaguar iPace + $40K for sensors and other AV equipment) for the car depreciated over 5 years, but $70K is the retail price for a Jaguar, including dealer markup, distribution, marketing, etc, and when you are buying thousands of them you are almost certainly not paying retail. Likewise, it figured 25c/kwh for electricity, which is retail off-peak PG&E rates, but Google just buys their own solar panels and pays pennies for electricity. The AV equipment figure of $40K was I recall what it cost back in ~2014; the cost of LIDAR has come down dramatically since then and now runs $500-1000/vehicle, so that number should also be suspect. And if vehicle cost is more like $50-60K/year than $110K/year, $7K/year in insurance is way too high. Hell, Google could just self-insure with their $250B in cash, they've got a stronger financial position than every insurer other than Berkshire Hathaway.

I'd bet the true cost per mile is well under $1.

[1] https://www.reddit.com/r/SelfDrivingCars/comments/1oiqerw/ho...

[2] https://www.reddit.com/r/waymo/comments/1il5d5i/unit_costs_p...

Engineering costs are capital/fixed costs, they're paid once to develop the technology and don't scale with the number of trips. Operating costs (which is what I'm discussing here) are what it actually costs to run each ride. Waymo's marginal cost per trip doesn't include a chunk of some engineer's salary.

Once there are enough trips, the fixed engineering costs are spread across more and more trips, exponentially trending towards zero, driving the cost per trip even lower.