As you probably know from my post about RICE - I enjoy buying some things in bulk. I do the same thing with flour for the same reason: It is sooo much cheaper!
I buy both All-Purpose flour and Bread flour at Sam's Club because that's where I find the best price compared to Walmart (or even Aldi!).
Walmart Great Value Brand 5 lb bag $1.72 = $.34 per pound
Sam's Club Bakers 25 lb bag $6.47 = $.25 per pound
What's even greater savings at Sam's Club is bread flour. It's within pennies of price to the All-purpose flour it's even more expensive at Walmart since Great Value doesn't make a bread flour (that I've found). Some people say that bread flour isn't any different than all-purpose but I do notice a difference so I always use bread flour when I make breads or pizza doughs (or whenever a recipe specifically calls for bread flour).
Walmart Pillsbury Bread Flour 5 lbs $2.88 = $.58 per pound
Sam's Club Bakers Bread Flour 25 lb bag $6.54 = $.26 per pound
Storing flour is super important. You cannot just store it in the bag it comes in. There is too much access to air - hence why flour can buff out the sides or top when you pick it up. Flour is one of those things that I keep stored in food grade buckets in our basement. I portion the flour in gallon size ziploc bags and put those in a lidded bucket. The absolute best way to store is to freeze the bags of flour (for two weeks) before putting them in the buckets because that kills any nastiness that might be hiding in the flour. My freezers are currently full so I can't do that this time... living on the edge and praying I don't regret it! Each gallon bag holds approximately 5 lbs of flour so that makes it easy to keep track of how much I have left.