Ann: EdenCrete Sales Update, page-90

pilko is probably in the ball park with his/her COG's . the actual material cost I feel is very low as it is just braking down methane (CH4) into Hydrogen and Carbon , and natural gas which is mainly methane sells for around $3.50 per 1000 cubic feet from memory

Possible cost of C:
Guess CH4 is Carbon with a mass of 12 and 4 Hydrogen mass of 4 so 12/16 * 53 pound of CH4 per 1000 cubic feet = 40 pounds of C per 1000 cubic feet of CH4
$3.50 / 40 pounds = 9 cents a pound of C
say a gallon of fluid weighs 8.3 pounds and C is 10% of the fluid weight so 0.83 pounds of C per gallon
0.83 * $0.09 = $0.075 cents of C per gallon of Edencrete

Welcome to be corrected on the above numbers please do not use for financial advice