Via select Alexa-enabled devices and for Prime members only, Amazon offers the Purina Yesterday's News Unscented Cat Litter 30-lb. Bag, model no. HS100, for $8 with free shipping. (To order, say "Alexa, order cat litter"; the link is for reference only). That's the lowest total price we could find by $8. (Local pet stores usually charge around $20.) It's made with recycled paper
Note: This discount is available only on Amazon Echo, Dot, Tap, Fire TV, and compatible Fire tablet devices.