Agreed.   
They're manufacturing them in England so no doubt it's a fairly small scale operation. Higher wages than Asia as well...It's a new product too. 
Nevertheless, even with the price of airsoft in Europe, there's no reason to be charging so much for it. 
  
A tracer unit must be more complicated or at least very similar in operation (same kind of thing; a sensor, a few LEDs. Shoved in an aluminium tube) 
£30 up to £100 for an expensive overpriced Madbull one but still not £120.