I live in the rainy Northwest United States and have seen these nifty 4-gallon square bucket panniers on some bikes over the past few years. A new pre-assembled pair will set you back about 90 dollars. I knew I could build them cheaper. Plus, I get way more satisfaction out of DIY products. For around half the price I was able to make my own, using brand new buckets and hardware. With a little ingenuity, you could save more scratch, it's up to you.
Here is what we'll be building: