Understand that you're paying for the skill, knowledge and experience of the designer. You're not really interested in just buying a website, you're really looking to buy a medium to increase sales. If you paid a designer to build you a website and that website didn't bring in new customers would you be happy with it? Of course not.
When hiring designers, writers or photographers, don't make the foolish mistake of thinking that they're all the same. Choose someone who's skilled, knowledgable, creative and has a marketing mindset. Remember, it's not creative unless it sells.
Marketing done properly will make you money; it's not an expense, it's an investment. It's the most important function of your business. It brings in new customers. It increases sales.