There is always more to say, but in this earlier answer I pointed out that Malian wealth was largely based on controlling goldfields that were not actually within the borders of the empire (if that is even a term that's applicable in this period), and also that there is some reason to think that the wealth that Mansa Musa distributed in Europe may have been saved up for up to a dozen years prior to the pilgrimage, and so did not necessarily really represent the GNP of the empire, either. You might like to review that response while you wait for fresh answers to your question: