Check your local Walgreens to find select Goodnites on clearance. I found size L/XL for only $3.29.
Even better, you can use coupons on top of clearance prices. Find a $1.50 coupon on the Goodnites website. Print it and use it in the store to pay $1.79.
To score a sweeter deal, use your available Walgreens Cash and make your purchase cheaper than $1.79, or even free.