All chains have limits - Countdown customers can buy four loaves at a time, New World and Pak 'n Save shoppers five.
According to the fine print in a New World advertisement in today's Herald, their discount price is valid until Sunday.
Countdown managing director Dave Chambers told the Herald last night the supermarket hoped to keep its $1 price for as long as possible.
"We can't set a date on it. Our ambition is to hold it as long as we can."
Factors such as an increase in the price of wheat could affect the newly-reduced price, he said.
The $1 loaves were part of Countdown's "price lockdown" programme which was initiated in October.
More than 430 grocery items had dropped in price as part of the programme, the supermarket said.
Mr Chambers said the company had "no idea" New World planned to drop the price of its Budget bread today.
"It's a competitive market. I've really got no idea of what their plans are. We've been planning this for a while."