Materials list and pricing for the cob oven.

500 garden pavers (used but in good condition) for base. free from craigslist but it cost 150 dollars to haul them. making them 30 cents a paver.
Sand from black lake quarry 500 pounds for 20 dollars.
Clay. 25 gallons dug up from friends property in the north end of the county (high percentage of clay in soil).
Fire brick 15. I was not able to find any used firebrick. new at 2.88 a brick.
Straw. 2 bails at 4 dollars a bail
Wine bottles. 20 free
stove pipe. used scrap metal, free