Though not a standard tree house, the vintage Boeing 727 was originally bought for $2000, cost $4000 to move it and a further $24,000 to renovate it and turn it into this Executive Suite 727 tree house. An interesting feature of the interior is the jacuzzi located in the cockpit.
14. Teahouse Testu, Yamanashi, Japan
This tree house is a mix of both minimalism and fantasy, with the interior being a simple, modern room, but the exterior looking it's been taken out of a page from a fairy tale.