Twenty-two Sydney monorail carriages are being sold on Gumtree for $3000 each, but will be nothing more than scrap metal if they are not purchased in the next week.

Harry Tsoukalas, manager of second-hand sales for Metropolitan Demolitions, the company that was awarded the removal contract of the monorail in 2013, put an advertisement on the online classifieds site last week in a bid to prevent the carriages from being destroyed.

"This is a Sydney icon and I don't want it mashed up and thrown in with the scrap metal," said Mr Tsoukalas, who is selling the carriages for $3000 each, about the amount he would receive from a scrap metal yard.

"It's very upsetting. When you know the history, it's so difficult for me to see that going to scrap metal.