Nonetheless William will one day be the legal owner of Balmoral and Sandringham and whatever Charles owns privately outside of the Duchy of Cornwall. In the broader context he will need a firm grasp of the Royal finances - both public and private. We can assume that he has an understanding of how his own personal trust(s) are managed and that his father and Duchy staff have provided some detail about the Duchy of Cornwall. He still needs to learn how the Duchy of Lancaster operates and in a future Sovereign to Sovereign transfer, which private monies and assets will directly and indirectly come to him.
Yes, there are bankers, tax specialists, lawyers, accountants, estate managers and advisers who know parts of the picture, but I'd imagine that each successive [modern] monarch would have a pretty firm grasp of what he or she privately owns, where those assets are located, the financial structures created to house and protect them, the various income streams produced, the overall cash flow, the nature of the private outgoings, the return on investment etc etc.
While this may be one of the more interesting areas to explore, it's unlikely that any of us will at any stage be any the wiser regarding the Windsor private wealth and its management. However, the extent, preservation and increase of the family fortune is a subject that Prince William will need to master. Doing so will take some time, and one thing we can be sure about is that there won't be a press release issued advising us of the fact.