The first recipe below would be very cheap to make with peat being 1/11th of the recipe and builder's sand is very cheap and usually sold by the yard. If you wanted a small bucket full, they'd probably charge $5 or just tell you to go grab yourself some, no charge. I also read recently that you can keep and reuse sowing/potting soil. Might need a bit of nutrients added back in. Lots of search results, https://duckduckgo.com/?q=reuse+sowing%2Fpotting+soil
With fertilizer and all prices going up, the prepper in me has been looking into making my own sowing/potting mixes from whatever I can obtain free or buy cheap. No luck on my first batch but I know some compost would have cured that lack of ability to wick up the water when bottom watering. Speaking of; noticed some white fuzzy stuff on the soil mix in my seedling tray which I think means it's headed for damping off. I pulled the cover off, wiped the condensation off the inside and left it off. White fuzz went away and I'll leave it off until later on tonight. Even though I bottom watered, the nix got too wet. It was shiny. BootsrapFarmer article says to learn how to go by weight of cell tray when bottom watering for best results.
Those soil mixes look delicious!
I broke down and bought 2 of the 1-cubic food bags of the Miracle Grow mix today, while it was on sale. ($9.37)
In the future I’ll buy the less expensive ‘Expert Gardener’ brand they have at Walmart. ($7.48 for the 1 CF size)
I do three hanging pots on my porch, so I want the Miracle Grow mix for those, as experience shows that stuff works GREAT in my hanging baskets, but I will mix whatever leftovers I have of MG and the Exp Gardener brand with clean soil that Beau is letting me have from his stash.
Other pots are just growing herbs and the tea garden plants I want and are less fussy than my hanging baskets can be.
Using those Jiffy Pellets for seed starting saves me a lot on soil, too.