Amazon has the 4-Pack Arm & Hammer Clean Scentsations In-Wash Scent Booster (24oz; Purifying Waters) on sale for $15.96 - 25% off coupon (check "Save an extra" box, eligible on first S&S order for this product)  - 5% off with Subscribe & Save (can cancel anytime) = $11.17 with free shipping on $25+ or with Prime. Roughly $2.79 per bottle vs. $4.97 at Walmart.