Pleasant, prompt and courteous service before and after the sale will make satisfied customers. You can control your image. Whatever image you seek to develop, it should be focused enough to promote in your advertising. One other thing to consider. Most businesses use a credit card system.
Some trade associations have a schedule for service charges.
Check with the trade association for your line of business. Their figures will make a good measuring stick to ensure that your prices are competitive. And, of course, your prices must be competitive. You've already found out your competitors' prices. Keep these in mind when you are working with your accountant.