If you want to construct your very own man space at the end of the garden then forget about a shed because the Concrete Canvas Shelter ($30K) is your new building of choice. Likewise, if you feel like retreating to the woods for several years then this could make a great ready-made home that can be moved around.
The Concrete Canvas Shelter is a product from British company Design Spotlight and comes in either 270 or 580 square foot variations. The shelter is a building in a bag and can be put up by two people in under an hour. Once constructed they are semi-permanent structures that come out of the pack, can be inflated, and are completely impervious to the elements. It is essentially an inflatable inner that sports a cement impregnated fabric around it, making it insulated and sturdy.
Amazingly, in theory the shelter can stay standing without maintenance for 10 years, while it can be outfitted with just about anything you want. Perhaps a garage for your motorbikes, an arms bunker for your next attack on rebel forces, or even a comfy living space complete with cable and Xbox. Basically whatever your particular thing is, you can do it in this shelter. If insulated with thermal mass such as dirt, it is possible to turn the CSS into a durable bomb shelter, so this structure also has some serious applications.