Dancing-Hot via eBay offers this DIY Cardboard Virtual Reality Toolkit for $2.45 with free shipping. That's $20 below our June mention of a similar kit and the lowest total price we've seen for such a kit. (It's currently $3 under the lowest total price we could find for a similar one.) Like the Google Cardboard, this kit includes everything you need to turn your smartphone into a VR headset: pre-cut cardboard, lenses, magnet, Velcro, and a rubberband.
Note that this item may arrive as late as January 2015.