This is how I make potting soil:
Pick up 1 yard of potting soil from local wholesale nursery ( pine bark mulch, peat moss, perlite)
Add extra bag of perlite (4 cu ft I think)
Pick up 1 yard of organic top soil from second place. (Mostly compost mixed with native soil)
Mix in 25% partly decomposed pine bark fines (left over from a pallet I ordered 2 years ago)
Yield 2.5 yards : cost approx $200.00
I up potted from 3 to 10 gallon about 40 pots and potted to 3 gallon another 30 starters.
Pictured are about 180 pots with more to come. Hopefully I have enough soil.