$13 for a set is a steal. I end up buying individual strings, or occasionally a 4 string set and a separate B to go with it. Just the B string can run $13.
My real suggestion for saving money on strings is to buy sets of strings that are, out of the pack, too bright for your taste. Every string loses some zing in the first hours or weeks of play, and after that settles into a long, relatively stable period where its sound is less bright than when new, and the change is very slow. If you buy strings that are the right amount of "too bright" when fresh, you'll get a lot of usable life out of them. Long string life is the key to saving money on strings.
People who complain that a set "dies fast" are mostly buying strings that sound good out of the pack, but when they settle in a short time later, they're not bright enough. Their string didn't "die fast", they just bought the wrong strings.