Effort = Accomplishment³

giving an exponential curve. I think the "curve"="graph" just makes more sense than "curve"="a bend in the road", but how can a (graph)curve be steep? The average gradient (or a straight line) can be steep, but not the curve itself.
I've always taken it to mean the amount to learn is a lot for the time available, whether that be a simple task in 5 minutes or a major skill in two weeks.
But I agree, it has become a cliche, and we should avoid cliches like the plague.

Rod