If you read my article you will see that my calculation is conservative in many respects, and that one of these conservative assumptions is a constant population. In the article I also define the concept of wealth levels.
I meant in terms of how it would translate to todays wealth as you mentioned 10 would be roughly a billionaire. Just for my own interest as it gives me an idea what to aim for

It would be very difficult to consider without a constant population but is one of the key flaws, still for something as a kind of loose reference point and to help people understand what their bitcoins could be it is a nice project
