The main difference through my research is food grade vs pharmaceutical grade. BRS is going to mix better because it is a higher grade. You really have to check labels to make sure there are no additives. But I believe if it says 100% soda ash and that it’s food grade it works the same just mixes a bit differently. If it’s 1/4 the price or greater then it’s a huge savings. BRS has built their empire on something this simple. Basically charging 4x the amount, but kudos to them. Because nobody else doing it. They do have the best two part mix in my opinion, but there are cheaper options.
I’m just curious if anyone is or has done the DIY. I think there are much better options to buy as to 10-15 years ago.
Another option would be to do a group buy. Buy 50 pound 100% food grade bags and divide. Would be dirt cheap.