Unless public transit is frequent and ubiquitous, it can't replace a car regardless of price
When I moved to San Francisco, an unlimited Muni pass was so cheap ($35) that it may as well been free, but I still had a car because weekend service is infrequent, and didn't go everywhere I wanted to go. I thought about giving up my car, until I tried an out of town trip on BART one weekend, it would have been an hour (or less) round trip by car, but since it involved a train transfer plus a long wait for a bus (that never came so I ended up walking the 2 miles), the transit part of the trip ended up being being over 3 hours.
Even now an unlimited Muni pass is cheap ($70), much cheaper than owning and parking a car in the city so it's not the cost of transit that makes people hold on to their cars.
On the other hand, when I spent some time in Tokyo, a $170 monthly Metro pass was much better than having a car, few of my friends who lived there full time owned a car.