As a finance professor, I am always interested in the business side of the small retail operations. A lot of times, I find that the owners are willing to share some of the details of their operation. Next time you are in your local running shop, ask the owner what they pay for rent on a monthly basis. Then ask them how many pairs of shoes they need to sell just to pay the rent. Of course, they also have to pay for lights, heat, garbage collection, water, inventory financing charges, bank fees, salaries, etc. Very few running shops are cash cows generating huge profits for their owners.
Personally, I believe in supporting the local running store, but I also know that I am in a position where financially the $10-20 difference is not a big deal to me. In my younger days, I was certainly much more price sensitive than I am today, and I was more inclined to use a catalog service.
My local running store hosts Sunday morning runs every week at 7 a.m. The owner has a rotating out-and-back courses with maps available for newcomers. He also goes out early to place water and gatorade along the course at 3 different locations. When everyone arrives back at the store after the run, he has free bages, juice, and water available. He charges nothing for the food or service. I would gladly pay him a weekly entry fee if he asked. He doesn't, so I view my payment in the form of my business and referral of my friends and colleagues.