The bar soap I use for my homemade laundry detergent is on sale this week at Walgreens for $.69 a bar! There is a coupon in the circular that will allow you to get up to 3 bars at this great price. You can regularly get Yardley soap for $1 a bar at Dollar Tree, but at this price 3 bars will only cost you $2.07.
I'm planning to get 3 and then make a "triple batch" of laundry detergent. I put my detergent in an old mayo container and then I have enough to last me a good 2-3 months!