I am North TX so we have the same issue. Its Austin and the indicative quote is $2150 plus your age divided by your birthdate
as these things always are.
I have a special compartment built on the side of the van for a single Honda but 2 requires a rear hitch mounted panier which has security issues in a lot of places I have to park overnight.
This last weekend the twin Honda set up was not sufficient to keep the Starcool running 100% of the time plus charge the battery with the fridge and the CO detector operating. After 2 days of this regimen and running the fridge for 2 nights, on the morning of day 3, the battery voltage was down to 8 volts. It recovered once I found a 110volt outlet. The OAT was 107 at 3 pm on both days and the interior temp was 87, better but not great. Parked on aspahlt with no shade whatosever.