I think there's a Factor X here that the statement "higher risk activities should pay more" misses, and that's the inherent popularity and attractiveness of the different activities.
Not necessarily how fun they are while doing them -- since that's all relative and personal anyway -- but their inherent draw to people who aren't currently engaged in them; how much they tend to "sell" themselves to players looking for something to do, if all else was equal, when looked at across the game as a whole.
And there are BIG disparities in how inherently engaging and attractive different activities are in Elite.
Combat and bounty hunting needs (needed?) its payouts buffed, no doubt.
But it's also probably the most fun activity in Elite, or at least it's probably the most attractive and intuitive activity to fall into doing. High-adrenaline, visually-arresting thrills. I'm talking, in general, across the whole game and userbase here (with some guesswork, I don't have the figures, FD does I'm sure).
Mining, trading... not quite so sexy. Satisfying once you actually get into them. But their inherent attractiveness lies more in the promise of big cash rewards, whereas combat has a bigger slice of excitement and adrenaline in its psychological rewards pie-chart.
I think it's perfectly reasonable for activities that don't sell themselves quite so readily (to people not currently doing them) to use higher rewards as a draw to get people involved in them.
Risk should also be a component in the decision-making over reward. But not the only one.
It needs to be a balance of these two things and more, IMO.
