> but I don't think that requires $500m in investment
Honestly, $500m sounds like a wild underestimate for what it would take to get last mile drone delivery working. Remember that this is something that's currently (mostly) illegal! There's clearly a lot of work to be done.
I don't think the fact that it's mostly illegal would discourage Uber. But compare it to Uber Eats: those driver subsidies, they're never going to get that money back. A drone last-mile R&D budget could at least lead to something. Even if it's imperfect and still requires some labor, maybe it vastly cuts cost. E.g., drivers are assigned drones, and they go from the driver's car, parked on the street of the destination, and fly to the front door to drop the food off, so drivers get more throughput while running their deliveries.
Honestly, $500m sounds like a wild underestimate for what it would take to get last mile drone delivery working. Remember that this is something that's currently (mostly) illegal! There's clearly a lot of work to be done.