Well I think there are two counter points: Uber already has a running business, so it's relatively easy for them to go to a bank and say 'Here's how much a fleet of cars cost, here are the running costs, would you finance us $3Bn for it'. The answer is almost certainly yes, and if not then venture capital would probably fill the gap.
The second point is that there are two keys to making money out of this: Have self-driving cars, find customers to rent the self-driving cars. Uber is already established in the second part. So it might be true that another company buys the cars and tries to run the business, but uber has the established customer base.
In my opinion the future of self-driving cars inevitably ends up with one of the big players buying uber to allow them to monetize their fleet.
The second point is that there are two keys to making money out of this: Have self-driving cars, find customers to rent the self-driving cars. Uber is already established in the second part. So it might be true that another company buys the cars and tries to run the business, but uber has the established customer base.
In my opinion the future of self-driving cars inevitably ends up with one of the big players buying uber to allow them to monetize their fleet.