If the extra cost is $2000 and a solar equipped car will recoup at best $50/year as OP stated then $2000/$50/year is 40 years to best case time recoup the cost

If the extra cost is $2000 and a solar equipped car will recoup at best $50/year as OP stated then $2000/$50/year is 40 years to best case time recoup the cost of the panels. Also you don't seem to be aware of this but $2000 is a lot of money to some people -- It's more than they spend on personal transportation.