At last week’s Google I/O conference, Google demonstrated the Google Cardboard VR kit. a concept that uses your smartphone as a VR platform. The kit basically acts as a frame to house the phone to be used as a VR display mount. The kit consists of a piece of cardboard, two lenses, a few magnets, an NFC tag and some velcro. It goes with a companion app called the Cardboard app.
The unassembled kit costs $30 but availed of 10% discount (google it) which reduced the price to $27. This is quite good considering cost to acquire the components individually and also time saved in preparing and cutting the cardboard.
They also have assembled kit for the same price.
This looks like an inexpensive way to play around with VR application without significant upfront investment.