I use purex dye and sent free. I bye from 2 sales once a year. Walgreens and Kroger put the 100 load on sale for $2.99 towards the end of the year. At Walgreens They give you points and store money for each so my price is $1.99 each. For Kroger sales, I price match at walmart because I don't have any here and print coupons for $1.00 off from several sites. Kroger puts both the 33 load and 100 load on sale in two different weeks for the same price. Near Christmas I look like I have more soap than I could ever use and by October the next year I am down to about 5. Some items you just have to stock up on when you can find a decent price.
Sounds like a good game plan!