The arguments for or against it being possible to earn a billion units of currency seem to hinge on differences in understanding of the term "earn".

The pg view seems to assume that if there is a causal relationship between your actions and a billion dollars appearing in your bank account, then it counts as having earned that money.

The countering viewpoint seems to consider the words "earn" and "build" as having a similar relationships to money and buildings respectively. If I tell you I built the shed in my garden, then you'll probably take my word for it. If I tell you I built a skyscraper, you'll either call me a liar or understand me to mean that a large number of individuals built it at my request.

I think the second version is more useful and more accurate.