A: The reason why the onion shot was so expensive is mostly down to my insistence that we do the job properly and as safely as possible. Pyrotechnic effects are very dangerous things so these things have to be done right.
To do it, I used Le Maitre Microdets - a box of 12 costs nearly £60 from Stage Electrics. I chose this method over any other because with a theatrical pyrotechnic like this, it's nearly guaranteed that when you press the fire button, the effect will work.
To make it all work, we hired in the rest of the equipment - the special firing box and all the cables to make it work. The firing box has it's own set of safety mechanisms - It won't go off if the circuit isn't correctly wired up, and to arm it you have to throw one switch and turn a key to activate it. It's much more technical than lighting the blue touch paper and standing back.
and I also had to go to Bristol to go and get the kit. so it all adds up to roughly £70 per shot.