Those numbers seem quite consistent with what I wrote. Costs per mile of a "normal" car today of about 50 cents/mile. (Which is approximately the IRS reimbursement rate so that seems very reasonable.) So that would be a good ballpark. Which is 1/2 to 1/3 of Uber today.

Sure, you can speculate about optimized taxi designs (which aren't especially relevant to non-core urban areas with high car ownership today) but small electric vehicles could exist without self-driving too.

IMO this is an academic exercise for at least a couple of decades in any case but it's an interesting thought experiment.