Real estate firm Barfoot and Thompson said the average price of a three-bedroom house in Meadowbank last month was $1,144,292.
Peterson said a first home buyer would need a 20 per cent deposit of $228,858 to buy the house and, based on Kiwibank's mortgage calculator, would then have to pay $1085 a week on a mortgage - impossible sums for the average family.
"All those thousands of people who will come and look at the house at the weekend but no one will actually have a chance to buy it," he said. "The people who will buy it will be investors or from the upper end of town."
The protesters will meet outside 200 St Johns Rd at noon on Saturday and will march to The Block open home at 97 St Johns Rd.
A spokeswoman for Mediaworks, which screens the show on TV3, said the company had no comment to make.