This shockingly large number comes from Matt Tuter, international projects manager at Family Radio--the California-based Christian organization that falsely predicted the world's end this past weekend--in an interview with the Christian Post.
The bulk of the $100 million, Tuter insists, came from selling off property (their KFTL television station and a FM station), although there appear plenty of people who donated their life savings to the cause. Tuter, whose family first got involved with the Family Radio organization when he was a baby, was also sure to clarify that "I remember when the organization was normal!" Apparently, this was before Harold Camping became a Doomsday prophet. Tuter adds that Camping "has actually made at least 10 predictions for the end times, though only a couple were announced publicly."