Comment by roughly

I think the point is to create uncertainty, though, or to at least capture it. You mention tacking a plus/minus range to $50, but my suspicion is that people's expected plus/minus would be narrower than the actual - I think the primary value of the example is that it makes it clear there's a very real possibility of the outcome being negative, which I don't think most people would acknowledge when they got the initial positive result. The increased uncertainty and the decreased confidence in the result is a feature, not a bug.