[Costco] Energizer Ultimate Lithium AA & AAA $19.99 per twenty ($1 per battery) YMMV IN-STORE
That makes them $ 0.74 each. But even for $19.99 it is a super deal, as far as on Amazon AA's are being sold for $46.99 per twenty.
Just for those who do not know – these are lithium batteries (the best chemistry available for AAA's and AA's).
They are super-efficient, do not leak, have a shelf life for around 20 years (mine are until 2039) and are made in Singapore.
UPD 6 Jan 2020: Updated the post. Now Costco sells them not for $14.99 per 20, but for $19.99 per 20, but still, it is a great deal as the price per battery is $1, while for example, Amazon sells them for $2.25 per battery (in the same 20 batches).