The trick is charge more. I don’t do what I would call heavy commercial such as restaurants, but I can’t imagine anything at any Burger King I’ve ever seen that I would do for $475.
If I were looking at the Burger King in my town I would have to rent a hot water machine - charge more. I would have to work at night which I don’t like to do - charge more.
I might do the 1,000 or so square feet of sidewalk attached to the building for $475 but that alone wouldn’t make it worth my while for all the hassle above. They would have to want more cleaned and that would cost more.
You don’t say what all you contracted to do but next time don’t sell yourself short. On a more positive note, I’m glad to see you picked up some work.