I went the other way, use cheap inputs for building my soil, stuff I buy by the bushel for the most part. Then when the cycle is finished I save the soil for tomato pots and when that’s seen a cycle I toss it. It’s a hybrid of ways, use organic until about the 30 day mark and then synthetic nutes from there on out. It keeps the soil volume from having to be too large for a truly organic grow. In my best estimate you’d need a 15 gallon soil for each plant at about 6 week veg to go the distance for water only, maybe it’s different but going organic means going larger.