I am propagating a lot of trees and shrubs and the cost of pots is something I looked at. I decided to get a big roll of heavy landscape fabric and a sewing machine for my oldest daughter. I got her to make bagged pots. There are youtube videos on it. Very easy to do, a project we did during winter months. The advantage was that as I used them, I could get her to make them in different sizes to suit the tree or shrub that I was growing. Also to advantage, they last a few seasons! I reuse them as well.
Tip: Don't skimp on thread, leads to much sadness