Yes. He is saying as you become more competent using excel, the efficiency increases exponentially.

Probably true for smallish values of competency, but it must be logarithmic after that.

To paraphrase for Guar, he's asking whether someone means "exponential" or exponential. By "exponential", I mean my feelings.

probably a sigmoid function

Being obtuse is not a desirable attribute, less so deliberately.

Asking people to say clearly and concretely what they mean is not obtuseness.

Nobody here has been able to elaborate on the initial statement "The efficiency gain vs learning curve is exponential". People are just rewording the sentence slightly and passing that off as an explanation. That seems to indicate that nobody knows what the statement means because the statement is vacuous.

It's mostly hand waving, but I think the OP was trying to point out that at the low end, a modest investment in training/learning gives great results in efficiency.

This is true! Then you hit a pretty hard wall with the limitations of the tool.

I think it means the efficiency gain is exponential (assuming the learning curve is anything less than exponential).

In the traditional, original sense of the term, learning curves are (presumably) asymptotic to a horizontal line representing total competence.

Somehow, sloppily, "steep" has come to mean difficult to learn, rather than quick to learn.

In the original version: A steep learning curve means quick learning at the beginning. A shallow curve means that it takes a long time to build up skill.

You're just rephrasing nonsense. What is "the efficiency gain is exponential" supposed to mean, in concrete terms? This is just empty manager-speak.

/s