Amazon offers Prime members the Safer Brand Ringer Lawn Fertilizer 25-lb. Bag, model no. 9333, for $24.16 with free shipping. (Non-members can spend $49 to bag free shipping; otherwise, it adds $19.17.) That's the lowest total price we could find by $10. This fertilizer features purports to be odorless and covers about 5,000 square feet.

Of note, shipping may take one to two months.