> the victims would assume it's a toy rather than the real thing, and so it wouldn't be as effective of a threat.

I dunno... I was once mugged by a guy holding a gun that I was probably 95% sure didn't work. It was a pistol that was rusted and filthy and looked like he'd found it in the ocean or something...

Nevertheless I have him what (small) money I had.

I don't think a lot of people are willing to risk their life on the chance a gun might be a toy, you know?