Well... absolutely the first rule of a profitable business is to know your market.

That said you have to do what it takes in order to make a buck. It also doesn't mean you have to sacrifice quality. It just means you can't offer the same level of attention that you would a $300 detail. At the prices you are stating you know that your competitors aren't doing the whole shooting match, find out what they are doing and best them. You can still offer the best $100 detail in town.