Some language and tool cultures have a very high CostOfLearning. Oracle, Java, C++, Vim, and anything for which there is a certificate beginning with the letters MS come to mind. Others have a lower CostOfLearning - present winner is probably Ruby.

CostOfLearning is related to whether the culture is ExtremelyInterstrangled and consequently whether its underlying language(s) have much SymmetryOfLanguage.

What other factors are involved?