Cost effective and effort effective are relative. Make sure you understand all the costs (glue, bottom boards, keels, paint, eyes, etc), and the long term durability of whatever you make......... and understand the effort quotient. I made a small rig of brown cork bobtail diver decoys this summer. Look good, ride well, and are very effective. BUT, the time I spent in filling and getting the brown cork sealed was more than I would have spent if I carved them from cedar. The cost of oils and eyes was the same as a cedar decoy, and I used a lot more glue and sealer than I would have to with cedar decoys. When and if I retire them in five years, and sell them, they probably won't bring half what the same decoy, made with cedar would bring. So my time, and up front cost are about the same, but resale is a lot less. so why cork? the biggest reason is, if a buddy rakes them in shot as the bluebills go through, they float just fine, I take them home, fill the holes, touch up the paint, and life goes on.
The biggy most of us focus on is the cost of the materials for the bodies and heads. We often forget other factors such as glues, eyes, special other items like burlap, mastic, sealers, primers, etc. The factor easiest to forget is the decoy's value in five or ten years after we make it........... Three other factors are your needs, finances, and ability to scrounge. If you need four dozen magnum decoys by this fall, you are trying to do it on a thin budget, and you are a great scrounger, procurring materials for free or at salvage prices, foamers are probably the answer. If you want to build a rig that you gun for years, you don't need to turn out lots of decoys in a short time, and want a rig which appreciates in value over the years, then maybe you need to look at other options.
I know of a guy who gets his body foam pieces from a contractor friend, so he pays nothing for it. If I buy foam board at the local Menard's, it costs much more per decoy. But when we are both done, they are still foam decoys. They can be artistically done, and they can float well, but if you ever want to sell them, or put them on the shelf, they are, well, foam.
I have used brown cork, western cedar, and northern white cedar with white pine and basswood heads, I have also molded decoys with Decoys unlimited molds and styro beads. A good paint job takes time and materials, whether on foam, cork or wood. Glass eyes are pricey, even if put them in decoys where the foam was obtained for free. I personally wouldn't "eye" basic foam decoys, but that is just me...........
In my opinion, wood, if properly chosen for the use by specie, is probably the most durable, and the most cost effective in terms of value over the lifesapn. When you retire well made and crafted wooden decoys, they are very saleable, and if you become very good at shaping bodies and heads, they are not that much slower to make than cork, or even foam decoys. If you cost it out considering durability and future value potential, hollow wooden decoys, with glass eyes, well crafted and painted in oils, may be cheaper than foamers made with free foam.
This is especially true if you can find local sawmills that offer good white pine, basswood, and cedar in desired sizes, that you can buy direct from the mill. I had good results from Western Cedar when I could get it cheaply from Menards and other dealers, but it has gone up in price to the point I can actually get midwestern cedar cheaper, and in the dimensions I want.
I am not being disrepectful of anyone who loves their cork or foam decoys. I've seen a bunch I admire greatly, and they ride the water great. Plastic foam decoys are a great way for persons to start carving their own decoys without needing specialized tools. They are a great way to learn to shape and paint decoys, even how to configure them to ride well. I'm just saying that hollow wooden decoys are something special when in use, and valued by collectors and family members when retired........... Wooden birds also bring out the best in me, encouraging me to do a little better paint job, and refining the shape, detailing, and pose more, anticipating the final judge of them to be humans, 10 or more years down the road, not ducks in front of me now........
But that is just me, and I'm sure I'll have many disputing it.
