In terms of dollars you should obviously expect more return by putting the same solar panels on a roof instead of a car - they generate the same energy and you

In terms of dollars you should obviously expect more return by putting the same solar panels on a roof instead of a car - they generate the same energy and you aren't adding mass to an object you repeatedly accelerate. But then you have to charge your car. The win here is convenience. If you average more charge per day than you average driving (and you have a large enough battery to load balance) you practically never have to charge (ignoring outliers like long road trips).