It can save you a ton on grocery bills. Bulk stores generally carry dry goods. We buy our whole grains, flours, dried fruits, nuts and beans, among other dry goods at our local bulk store. Between shopping once a month or so at a bulk foods store and shopping weekly at our local farmers market, we break the need to shop weekly at the grocery store. The less I go into the grocery store, the more we save. I have a tendency to pick up 'extras' when I grocery shop. I find we eat more healthfully when shopping this way too. (Quick note: I often find the bulk section at traditional grocery stores to be more expensive than actual 'bulk food stores'. Compare prices!)
Another nice thing about buying in bulk is that you don't have to pay for the exorbitant layers of packaging. Therefore, said packaging doesn't end up in a landfill. I like to take my own containers when I can so as not to end up with extra bags. Most of the above jars were actually a wedding gift from Target of all places. But jars from peanut butter, honey and pasta sauce work just as well.
One might think buying in bulk like this adds too much extra time to cooking. It can, but the money it saves, the health benefits of eating whole grains and unprocessed foods and the lack of packaging all make it worth it in my mind. There are also a few tricks to it. Prepare things ahead of time and in larger quantities. Then they can be frozen and defrosted at will. A crock pot is also a great friend. You can put things in before you leave for the day and come home to dinner already cooked. Prepared beans and rice both can be frozen and reheated as needed. I cook mine in big batches and freeze in small quantities. A tip for cooking beans faster: add kombu(seaweed) to the simmering beans. Remember to cook fully before adding any salt or seasonings. Sometimes that can inhibit the amount of water the beans soak up and leave you with hard beans. Yuck!
Once you go into a bulk store the possibilities are endless. You'll find interesting things to try every time you go in. Do keep in mind that prices change each month on various items. Once you've been going for a while you'll know when something is a good deal and can stock up that month.