Amazon has the 20-pack AmazonBasics Alkaline Batteries (AA) for $3.56 - 5% off with Subscribe & Save (can cancel at any time) = $3.38
with free shipping. AAA batteries
with S&S.Toys R Us
is having a Buy One Get One Free Sale on all Toys R Us brand batteries. Free in-store pickup available; shipping to home starts around $7. Add two of the pictured 20-pack AA Ultra Alkaline Batteries
to cart for $7
with free in-store pickup.