The Hexayurt is a prize-winning shelter you can build yourself for about $200 (backup link). Suitable raw materials include common building materials ( fire safe insulation boards,) hexacomb cardboard and plastic. You cut six 4′ x 8′ panels in half diagonally to make the roof, and use six more whole panels to form the walls. It takes about two hours. The design (backup link) is in the public domain.