Blackberry Cane or Plant

I didn't realise they sold blackberries as canes?
Raspberries are often sold as 3 or 4 canes in a pot. They each get planted out to form plants.

Blackberries will to the same, stick a cane in and eventually it will grow into a small plant.

I've not looked, but usually blackberries are only sold as plants? They can get more money for one plant.