All in all, you will probably get a lot more than $51/working day if you're able to get rid of your car if you start biking to work. And a lot more than money!
Of course, you might not be able to keep all that money. Even if your commute is how you mostly use your car, you might also need it for other stuff some times. Stuff you can do with a taxi and a rental car. This will eat some of the profit, but maybe far less than you think. And you can probably find ways to reduce this over time!