The biggest benefit I see to buying local is that, compared to an online retailer, you return almost fifty times the amount of money back to your community. This increases the wealth of everyone in the community. It decreases taxes because it puts less of a strain on infrastructure. It employs more local people. It fosters choices more in line with the values of the community. It creates a more cohesive community which leads to less crime. It is healthier because with the increased cohesiveness there is the tendency to address health problems more effectively and the food is better for you.
Buying local also increases the unique characteristics of your community which increases tourism. When you go on vacation do you eat at a chain restaurant or do you sample the local fare? Do you shop at Walmart or do you try the local shops who have a more unique selection? Do you engage in the cultural activities that only your destination has to offer or do you choose the same types of entertainment you can find in every major city? You choose the local color of course. Otherwise, why would you go on vacation? Encourage others to enjoy a richer cultural experience when they come to your town. Support your local businesses.
If you want to increase your wealth and the wealth of your community get involved with your local business alliance. They can help.