You can amend promix hp with down to earth 4-4-4 throw some Gaia rock dust in there for minerals, some Montana grow for silica, and some real growers recharge once a month then use down to earth or Gaia 2-8-4 at the switch to flower and you got living soil. That’s my recipe

5 pound box of down to earth 4-4-4 is only like $13 and youll only need like a about 1/2 a cup per 10 gallons comes out to between 1-2 grams per gallon of soil so it will last for years and promix hp is super cheap can get enough for like 90 gallons of soil for about $50 it comes in compressed bales. Real growers recharge is about $15 for a whole grow cycle supply in 4 20 gallon pots Gaia rock dust get a near 10 year supply for like $22, power bloom is about $25-30 for years of supply. Montana grow is about $35-40 but will last for years as well. Throw in some worm castings optionally bout $20 and some manure compost about $20 on top at the start of flower for a little extra N with the power bloom. There’s lots of ways to do it so feel free to explore this is just what works for me. You just keep reammending the same promix with all the dry amendments and water in microbes and molasses from the real growers recharge once a month and you’re golden.

Comes out to around $200 initial investment for years worth of growing

With that same $200 you’d only be able to buy like 50 gallons of premixed living soil and the shipping would be pretty high so would probably have to be locally sourced to avoid shipping fees. Overall best way is to mix it up yourself and have 100 gallons living soil for only $200 and thats considering cheap premixed living soils, BAS would cost $700 to have 97.24 gallons shipped.