That cubic meter of pre-made potting mix will fill 2,197 three inch pots. Seems like a sweet deal to me. That's about 4 cents per pot.
I make my own potting mix which is approximately 50% sandy garden soil, pasteurized to kill weed seeds, and 50% leaf mold
compost. I wouldn't add any type of wood product to a potting mix because the microbes trying to digest it sap the nitrogen from the rest of the mix. I don't use horse manure at my place because of previous problems with it being full of weed seeds. I suppose it depends on how composted it is already.
I don't trust the local suppliers of composts and potting soils to provide products that are free of industrial wastes, and pesticides, and heavy metals, so I make my own... Early on, weed seeds germinating were my biggest problem. So I started pasteurizing the screened soil at about 140F for a couple hours. I also had problems because the leaf-mold was not fully composted. These days patience is the name of the game for me when making potting mixes. I'll pasteurize the soil, and add the well composted leaf mold. Then stir it for weeks, keeping it watered so any residual weed seeds germinate, and then do some germination tests in each lot to make sure that the plants grow properly.
I think that sand and well composted horse manure would make a great potting mix.