Best defense against stolen bike lights: take them inside with you. It’s an OK design but does not seem to be very bright at all… they are just using basic LEDs, not any of the higher wattage CREE etc. stuff. Plus, batteries are not rechargeable, which is a big minus IMO. At least $50 is not completely unreasonable.
I have one that I superglued to the mount so that it would be a huge PITA to remove it. I also lost a screw that held part of it together and – because who wants to spend like 25¢ to replace a screw? – I just covered it in duct tape to hold it together. Shockingly, no one has stolen that one, despite how aesthetically pleasing it is. Maybe I need to start marketing that anti-theft system.
If you are walking around with the necessary tool you can swipe anything, Nothing is theft proof but the idea of making something more difficult to steal is a good idea. We use U-locks the same way not 100% but still difficult enough to prevent most thefts.
A battery powered saw or dremel can cut through a lot in short order. Not a fault of the designers, just poor wording. We don’t have thieves like that around here though, that I am aware of. I take my lights with me, except my PB Blaze 2w because it is a piece of shit that I hope gets stolen.