The Lucky Lotto Shop in Rotorua reported one customer spent more than $1,000 yesterday morning.
David Smolenski, who owns the Richmond Night N Day Foodstore with his wife Amber, said many people had doubled their Lotto spending this week.
"People who usually don't add Powerball to their tickets are coming in and adding it, which doubles the cost of the ticket," he said.
United Video Blockhouse Bay owner Harry Wadan said he expects big spending every time a Lotto jackpot balloons.
"The customers who put $3000 on tickets are the ones who only come in once a year when it gets really big and must be won."
Auckland University Associate Professor of Statistics Ross Ihaka put the odds of winning a $20 million windfall at 1 in 38 million.
"A comparable event would be if you tossed a coin 25 times and it came up heads every time," he said.