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.
If you want to go the low cost route Mike's Cool Stuff shows a design for doing this. It is fairly complex and requires detailed elecronics knowledge to create. He avoids using costly modules such as wifi, uses low cost camera modules and tackles subtle issues such as power drain, sequence triggers etc. <https://m.youtube.com/watch?v=Lvyslu65V3s>