How much does pain hurt?  

They say different individuals have different thresholds of pain. Does that mean one person may feel more pain from, let’s say, a toothache than another? Or does it mean one person is more able to bear a given level of pain than another?

And how can anyone tell what a given level of pain is?

As this article points out, “pain is difficult to describe and impossible to see. So how can doctors measure it?”