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Space astronomy is expensive! A large ground-based telescope of 8-10 meters aperture might cost $100-200 million. However, a complex telescope in space might cost$1-2 billion, even though it is only 2-3 meters in aperture. What makes the large difference? Space is an extreme environment and launch puts enormous stresses on scientific equipment. To make sure a space observatory will not fail in orbit, the components must be rigorously tested and often duplicates have to be built. NASA has recently experimented with more modest missions with a price tag of \$200-400 million. These telescopes have a simpler design and can not tackle such a wide range of astronomy. However, the cost of a single failure is not punitive. As large as all these numbers are, they are dwarfed by the projected cost of sending astronauts to the Moon or Mars.