Tomorrow, ALDI has a special on a pack of 50 AA or AAA batteries for $14.99 — an effective price of 30 cents each. That's a good price for bargain-basement batteries, but it's not the cheapest we've seen.
For instance, Kmart regularly sells a 24-pack of AA or AAA batteries for $5, which works out at 21 cents each — less than ALDI. Members of IKEA's free IKEA Family scheme can also purchase a 10 pack for $2.99, which is the same price as ALDI.
Whatever supplier, you might well argue that cheap batteries are less effective than expensive models which last longer, or prefer to use rechargeable batteries and reduce landfill. If you're happy with a cheap and cheerful battery and want a plentiful supply, this is a reasonable but not astonishing deal.