How about driver time? Filling up a gas tank compared to waiting on the truck to get recharged.
Drivers are required to take a break after 8 hours. If you can get 500 miles to coincide with the break you could charge then. I do not know the recharge time.
Seems most of the orders for the Tesla truck are from companies that utilize a lot of short haul, Pepsi being one. They would probably be cost effective for someone like that.