Slow day at work for me and this is interesting.
As for the cost, that's why you'll need a good form of public transportation in place. Those who can't adopt take public transit. If you can't supply a satisfactory form of public transit allowing people to get to where they need to be without taking forever (a current issue with our system in Phoenix today) then people will leave. I'll be fortunate enough that in 3 or so years time I'll be able to buy a $120,000 car outright but right now I can barely afford to pay for new tires. There are a lot of people in the "I can't even afford tires" category that will require public transit. You can't force those people because they couldn't buy an AV if they wanted to.
As for the advancement of technology, you're correct but the ability to roll this out is still dependent on the costs associated with the technology. We are working on AV now but it could still be 20 years before they have developed enough to make it possible for the general population beyond level 2 autonomy.
Cell phones were a business device for 10+ years and were not a consumer product until the 80s. They also cost $4,000 to buy. It wasn't until 20 years later that it became a realistic consumer product as cost came down and technology advanced enough that it could actually fit in your pocket. Move another 10 years into the future when Apple and Android changed everything and a sustainable product was finally built. That's a 30 year time table.
You will see business adoption over 10+ years for level 4 from the drop date (lets say 2023), followed by 10+ years of sub sustainable AVs for consumers, and finally someone will perfect the technology in a way that the general public will be able to get on board with. We are 24+ years away from that today. I'll be 55 years old.. Cell phones should be the dankest s*** by then though! I'm sure I'll elect for the contacts, brain implant, ear implant, and finger sensors.
Public transit needs to be the #1 priority to remove congestion, AV is not the answer now or in the near future.
Also I know you used cell phones as a way to show we are capable of achieving this, I'm not trying to counter that. Just wanted to add my two cents.