Sounds like your clients aren't well grounded in the actual costs of conducting business.
It depends on the business. You haven't worked with community theater spaces, apparently. Hotels will take the absolute cheapest up-front option, ditto for most "event centers" and banquet halls.
Some of them have no existing infrastructure and the price difference doesn't matter. Some will never need to use this service with rental cables. Some need it "right fucking now" and the local electrician can install a 14-50R because there's one in the truck.