Me. I think I am underpaid (actually I think most devs in my country are underpaid) so i don't do it with the exception of when I made a major cock up and the team was waiting on me.
They're very likely in the UK.
They are very likely getting underpaid for dev work, unless they're a contractor. Our salaries are definitely lower here than in the states.
Has it? Seriously, who is this all powerful "market" that one can go ask and get an exact answer? What does "market" have to say about employers simply giving anemic raises, if they give any at all, to employees they believe will have trouble finding new employment?
Someone's current wage is not correlated with the market wages for their current position.
Its often the case that nurses and teachers are considered underpaid as well. While bankers are overpaid. Would you agree with that?