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: 
This is the product recommended by Chris Breeze and Eric Pare at Xangle amongst others - the Esper Triggerbox <https://www.esperhq.com/product/triggerbox/>

The ESPER TriggerBox is the world’s leading programmable multi-camera shutter release controller. Up to 6 cameras can be connected to each TriggerBox and it allows multiple camera to be fired simultaneously or with programmed sequences and offsets + multiple TriggerBoxes can be linked together to synchronise larger multiple camera setups and they neatly stack together, a bit like LEGO bricks! [![enter image description here](https://i.stack.imgur.com/YFFtf.jpg)](https://i.stack.imgur.com/YFFtf.jpg)
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.