A very easy to build crossbow.the stock is actually pine but the prod(bow)is pvc.the stirrup is just a piece of para cord so is the string but with some duct tape.the whole thing is spray painted silver.it shoots well and fast.all I had to buy was the wood which cost me about $5 in New Zealand(which is where I live).if you had to buy all the materials then it would cost $25-$30 I'm guessing.
Step 1: Prod
The prod is made of pvc.its the bow part of the crossbow.its just a 90cm piece of 20mm pipe flattened like you would make a bow.nothing fancy no recurves no anything just flattened pvc pipe.in fact I used a old bow
Step 2: The Stock
This toke about two hours to make.the wood is pine.the prod is lashed on with hemp twine.i added a pvc thing to hold the arrow in place. The trigger is a dowel that pushes the string up the string dosnt nock on to the bolt.
Step 3: Bolts
The shafts are pine dowels waxed with beeswax.fletchings are made of duct tape.the point is blunt in drilled a hole and then I glued nails in to them.i also added a groove for the string to hold onto.