I agree with what Simon says, it is over the top pricing, unless he had to drive 50 miles or so to apply it.
Some guys are just greedy, you can't give it away, but you can charge fairly. You could say that if the customer accepts your price no matter how over the top it is, then he's not being ripped off, but that is simply taking advantage of his ignorance, that's not smart or clever it's unethical.