Walmart offers the Penn Championship Extra Duty Tennis Ball 3-Ball Can 12-Pack (36 balls total) for $22.27. (Amazon charges the same for Prime members only, although there's currently a 1- to 2-month delay in shipping time.) Opt for in-store pickup to avoid the $5.97 shipping charge. That's 62 cents per ball, tied with our mention from two weeks ago, and the lowest price we could find for this quantity by $8.

Update: It's now available for in-store pickup only.