Cheap is in the opinion of the person making the mold. I do it this way......I take a duck body and cut it in half length-wise with a band saw. I lay one half of the body - frozen - on a rectangular piece of plexiglass big enough to hold the body and have about a 2" shelf all the way around. I make a plaster mold - doing both halves. I use old cheap eyes for the line up bubbles - this lines the mold up every time without having to keep adjusting it. Once both mold sides are made - I make a 3 pound foam body. Always drill relief holes in your molds, this way it will not explode on you when you over fill it. I take the new body out and sand it to the specs I want. The plaster mold will only make 1-3 before it craps out on you. I again split the body into two halves with a bad saw. Place each half onto a rectangular piece of plexiglass - usually the same ones from the plaster mold. This time I use fiberglass resign and apply a initial coat of about 1/8" to 1/4" WITHOUT and fiber added. This makes the area next to the foam smooth. This takes about 4-7 coats and in each coat after the first one, I add the fiber cut up into small strands and pieces. DO NOT use bondo - it will explode on you at some point. The resign cast mold will last forever. Be sure to drill two relief holes in the top of the mold. I also make the bottom half on the mold squared off so it will sit level while going off. I use "C" clamps - 4 of them - to hold it while going off. No worries if it oozes out of the holes, just cut it off. I think most duck bodies sell for $6-$10 and I can make one for about .25 worth of foam. You can do the same thing with heads. Just use the real head - bondo it back into shape and cast it. I use liquid rubber molding material for heads. I do not do too many heads - it is just easier to buy them, the rubber molding material is expensive and they only last a dozen or so heads before they start breaking down. Hope this helps.