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.
Breeze Systems makes [software for controlling multiple cameras](http://breezesys.com/MultiCamera/psr_index.htm) at once. It's worth looking at their site if only for inspiration.

Keep in mind that cheap cameras may not have a remote shutter release option; if this is for a one-time event, you might be better off renting a set of more capable cameras.