You're missing something important.
The rush hour isn't going to spread out enough to relieve congestion; people have been predicting that since the 1960s and it does not happen. No reason to think that'll change.
It's quite possible that prices will drop in the off-peak. But in the peak in a big city, it's *already* true that nobody who's in a hurry and can take mass transit takes an invididual car, to crawl through congestion at 5 mph. Buses are clearly inferior to trains, and buses in mixed traffic are already hopeless because of the cars getting in their way and reducing them to the same speed, but buses in bus lanes or carpool lanes (Market Street anyone?) still have an advantage over cars.
Think of the rich people who own 2, or more, cars and have been commuting on the LIRR for the last 100 years because you have to be insane to drive into Manhattan. Their cars are actually used by them *off-peak only*.
Now, this does raise a possible scenario: maybe I'm wrong about the price -- maybe ride share will be cheaper than the bus during peak hours *because it's worse than the bus*. People will be riding into work on mass transit and allowing their cars to be rented out at peak hours. Anyone who rents that car out will be caught slogging through traffic slowly at rush hour and will be getting inferior service to the people in the bus lanes -- so it'll cost less because it's inferior.
The fundamental issue is that rideshare cannot handle the commuting market. In the peak commute hours, either it'll be a high-priced luxury service for a few, or it'll be a low-priced junk service for those with a lot of time to kill, but there's no way for it to replace *mass* transit, because it can't move a *mass*. As long as there's a mass to move, the service which has the economies of scale will be the cheapest to operate and will have the lowest unsubsidized price. (And yes, trains do that much better than buses, but buses get the same indirect government subsidies as cars -- the subsidies for the asphalt roads -- so they'll probably hang around in the US until we start treating railroad tracks as something we should fund out of property tax. Incidentally this is also why Musk's tunnel company is doomed unless it goes for government contracts; it's very hard to run a profitable toll road against a large network of free roads funded out of property-tax, especially when your toll road has *tunnel* expenses too -- the only way to counteract that is economies of scale and he doesn't have them with cars.)
