The International Space Station
If you think keeping to construction schedules and budgets is tough on Earth, try doing it in orbit. That's the fiscal lesson of the International Space Station (ISS), an orbital laboratory that's a joint effort between Russia, Europe, Japan, Canada and the U.S. The project was so complex and unwieldy that it was already four years behind schedule when it began in 1998, and its original estimated cost of $17.4 billion ultimately grew to $160 billion. The U.S. kicked in $100 billion of that total [sources: Boyle, Plumer].
Add to that the station's operating costs, to which the U.S. has contributed $3 billion annually. Those costs seem even more massive when you consider the station's limited lifespan, which was set to end in 2020. In January 2014, the Obama administration announced that it would extend the station's operation until at least 2024 (subject to congressional approval), which may help taxpayers get more for their money. Even so, the ISS most likely is the most expensive single structure ever built [source: Plumer].