If you start driving for Uber with some vehicle that’s extremely expensive to operate, like a Land Rover or something, maybe you’d lose money, but that’s not the norm. It’s common for Uber drivers to finance their vehicles by driving for Uber. This obviously only works if there is a surplus of value created by driving that vehicle for Uber. It’s not like independently wealthy people are subsidizing Uber by donating the equity of their cars. The cost of cars used by drivers is ultimately paid by customers, there is not some magic trick here.