I don't think either company has turned a profit in the last 5 years at least. They're just spending VC money to try to kill the competition. That $4.3 and $1.8 billion isn't from profit, its from VC's trying to outspend each other.
I don't get their strategy. While they are an true tech company - the marginal cost of servicing next client is essentially zero, their network effect is limited to a single city so it will be easy for potential competitors to enter the market.