Or do the same from New Haven as I did yesterday. The garage is $13/day, it will probably be easy to find a space in it (though it being a holiday weekend may skew things a bit), and you have the option to take Metro North instead of Amtrak in one or both directions. If you want a late return you can do so on Metro North, departing Grand Central at 11:22 PM, arriving New Haven at 1:12 AM, at an off-peak fare of $14.75/person.