Miller's is a professional lab that caters to portrait and wedding photographers. Protecting their pricing is a service to the pros, as is their requirement that you sign up. As I said, they are top notch and very focused on quality and customer service. Atlanta no longer has any C41 labs so I was delighted to discover that one of my favorite suppliers still handled it.
Protecting their pricing? How? At first I thought to make it more difficult for their competitors but that cannot be, you state there are none in Atlanta. I guess it does not matter anyway. Just wonder about the logic.