Question: I want to assemble several cameras, triggered by a single remote. Is this possible?
The trigger doesn't have to be wireless, because the cameras will be very near to each other. The cameras need to be very cheap, because I'll be needing 50 of them.

Answer: 
If cost is a central concern, then you might want to investigate a DIY route. Using a platform such as [Arduino](http://www.adafruit.com/category/17), you can [purchase basic cameras](http://www.adafruit.com/search?q=camera&b=1), and using the Arduino board, trigger them together in a variety of ways...really only your imagination is your limit here. As most of these cameras are very small, it should be easy to pack them together.

I have linked to Adafruit for these items, but there are hundreds of vendors for Arduino or Raspberry Pi products.
It can be done with GoPro cameras, and the [GoPro wifi remote](http://shop.gopro.com/accessories/smart-remote/ARMTE-002.html). You can pair one remote to multiple cameras, apparently you can control up to 50 cameras at once. See [Controlling Multiple Cameras with One Wi-Fi Remote](http://gopro.com/support/articles/controlling-individual-cameras-with-the-wi-fi-remote-when-multiple-cameras-are-paired)

Though it wouldn't be cheap, if you need to buy 50 of them. The cheapest current model would be the Hero3 White edition, which has wifi built in. Or you could use an older HD Hero or HD Hero 2 with the wifi bacpac, but these are now discontinued and getting harder to find.

This video is a nice example of using 52 GoPro cameras for a "bullet time" effect. <https://www.youtube.com/watch?v=zKtAuflyc5w>