Employees work on the construction of a bunker at Utah Shelter Systems in North Salt Lake, Utah, December 12, 2012. The price of the shelters range from $51,800 to $64,900. While most "preppers" discount the Mayan calendar prophecy, many are preparing to be self-sufficient for threats like nuclear war, natural disaster, famine and economic collapse. Picture taken December 12, 2012. REUTERS/Jim Urquhart (UNITED STATES - Tags: SOCIETY BUSINESS CONSTRUCTION) Published: Pro. 18, 2012, 5:24 odp.