For those in the general Northwest region of the US, Concentrates is a good wholesale source for soil amendments at reasonable prices - particularly if you can get folks together to place a bulk order.
https://www.concentratesnw.com/

If you happen to be close to Corvallis, OR I organize a big nonprofit bulk purchase from them each winter for distribution in our community.

Soils in the arid west tend to be alkaline. Soils in the rainy northwest tend to be strongly acid due to leaching. Soil tests are definitely worthwhile. Sometimes there will be a serious deficiency of some micronutrient like boron, with remarkable results when it is corrected.

This thread seems to have changed direction significantly :-)