thx for the chart. Not sure i can completely understand the meaning. Pity that the home brew has little stats, but the comparison between the commercial suppliers is startling. Still, i dont know what this all means in the long run. No matter how you do the math, it costs more to buy commercial product even tho it may be less effective, but how much do we really need. Thats one reason i cant help loving Bob Beck, he really seems to care about keeping the cost within everyones reach. Commercial operations today no longer consider this!!!