In this scenario, Uber should be able to maintain their own cars at a lower cost than individual car owners can, due to their scale. They would also probably be able to buy the cars for less to begin with.

Keeping in mind that Hypercar would have to pay car-loaners at least the amount that the car loan is costing them in maintenance & depreciation (or else who would loan their car), Uber would come out ahead.

Maybe in the short-term, this Hypercar company could rely on car-loaners to underestimate maintenance/depreciation costs but surely that would only last so long.

Isn't your last sentence also entirely true of Uber's current business model?

if "Uber should be able to maintain their own cars at a lower cost than individual car owners can", then Uber should be buying cars today and leasing them out to their contractor drivers. Truck fleets do this, pretty much, so it's not a completely crazy idea. Uber isn't doing that, which suggests that Uber thinks its a better deal for them to have their drivers shoulder the ownership, maintenance and depreciation costs of the capital. Why does self-driving change this?

Only reasons that seems to make sense is because people think that Uber is only compensating their drivers for their labor - but they're not; they are compensating them for their labor as a driver plus the lease and use of their car.

Without self-driving cars, there's not a good way to have contract drivers who can just work whenever.

In German Cities Car Sharing is becoming very popular and a lot of Manufacturers have introduced their own car sharing offers or formed Partnerships with existing Companies. Tesla probably would do the same, because otherwise they would risk that Uber buys their cars elsewhere next time.

Your ignoring time value of money. Car depreciation is far from 1:1 with miles driven.

Also, I might need a self-driving car to do a 60 mile trip to work and home every day. But, during work I may be better off letting the car drive others than pay for parking.

One issue with this scenario - once Uber is no longer paying drivers, it should become a lot cheaper, making it viable for a lot more people to get rid of their cars and just rely on Uber. So that'd decrease the pool of people to loan their cars to Hypercar. Effectively everyone would be "ride-sharing", but through Uber.

And then Uber, owning this fleet of cars, would be disrupted by a company that sells/leases self-driving car kits to people who then convert their own vehicles into robo-taxis.

People seem to miss the part when Uber has a lot of mindshare and users with the app already installed. That is part of why they are valued so heavily. There is a giant and obvious market out there and Uber won't be competing on even ground since they already have their app installed in so many places.

When switching costs are low that mindshare isn't worth too much.

All rental companies keep their cars for one or maybr two years and then get rid of them. Nobody wants old cars in their fleet and I suspect uber will be similar.

I think they will end up like airlines. Not a great business to be in.