BigW has 9v batteries marked down. Original price was $6.50 per 2pk. Shelf ticket stated $5. Scanned at the register as $3. Apply family & friends discount for $2.70 price.
Other alkaline batteries also reasonably priced.
20pk AA @ $4.50
4pk C @ $4.50
4pk D @ $6.30
Prices above include Family & Friends discount: http://www.bigw.com.au/familyandfriends
But I reckon the 9v in particular is still pretty good at 2pk for $3 after that expires.
I think you will find the $1 batteries are carbon zinc, not alkaline. So they would have substantially lower power and shorter shelf life.
This deal indicates they are "Extra Heavy Duty" instead of alkaline, and that the $1 deal had time and quantity limits:
https://www.ozbargain.com.au/node/97978
I'd be happy to be proved wrong, I have been looking for cheap alkaline 9v and they are seldom available under $2 each.
from my understanding they no longer stock the carbon zinc batteries, only seem to stock 1200mAh ones (http://www.batteryworld.com.au/battery-finder-results?keys=s…) could be wrong
1200mAh suggests those are lithium batteries (reference: http://en.wikipedia.org/wiki/Nine-volt_battery)
If they can be had for $1 each it would be a super bargain, as they are usually more like $10ea!
i saw woolies also has their Chevron lithium AA and AAA on sale too. cant remember the exact price but were $4 cheaper than the energiser equivalent (plus the energisers were $% off to start with).
Not exactly a deal, battery world have $1 "smoke alarm" batteries which are just the same as these year round. http://www.batteryworld.com.au/store-list