Coast Guard is made to do salvage missions, many more important than this one. The cost of doing a mission like this is not large compared to the cost of acquiring and maintaining the equipment and crews necessary. It's good practice, good PR, and may give technical insight that will be useful to civilian or military engineers working on deep-sea submersibles.
Basically, we've already spent 99% of the money necessary before even considering whether or not to undertake a particular salvage mission. You already bought the car - what's a drive down to the next state over, really? Gas and some wear and tear?