When a Manhattan resident needed another bedroom, the only obvious option was to build up, using a recycled shipping container. Not only did he save money, but he gained a view of the Empire State Building in the process.
Measuring 6m in length, the container was turned into the new master bedroom and also turned the scrappy roof into a nice patio area. While the architect Lot-ek hasn't made the overall costs public, I imagine it's one of the cheapest penthouses in the whole of Manhattan - and with a view of the Empire State Building as well! [Lot-ek via Inhabitat]