As of a late 5/14/17 re-check, the price jumped close to $20…
The AmazonBasics 100-pack sale ended, but the 100pk of AC Delco single-use AA batteries continues to drip, now down to $12.56 at Amazon by Amazon itself, with a limit of one per customer, and currently restricted to Prime members. Or if you are willing to do a “Subscribe and Save”, the price drops to just under $12.
At the $12.56 price, it comes out to 7.96 batteries per $1. Let’s just call it 8 🙂
UPDATE: if you don’t need that many, you can get an 8pk of Energizer MAX AA Batteries for $2.22 after a 50c off clip-on coupon.