Dumpling $15B on the market should lead to a drop. Anyway, the gold price is not always going up.

The claim is that rising gold prices lead to gains of $15b. As in they started with 129 tons of gold in the US, then they sold that and bought gold in Europe, and in the end, due to rising gold prices, they had 129 tons of gold in Paris plus $15b extra cash. Please explain a hypothetical course of events which makes this plausible.

Keep in mind that 129 tons of gold is worth just a bit more than $15b, so small market fluctuations on the scale of 10% isn't enough by itself.

They purchased 129 tons of gold in Europe. Their asset position did not change: they converted cash to gold of the same value.

They then sold the 129 tons gold in the US vaults for $16 billion. That gold was originally purchased I'm guessing many decades ago for $1 billion. The have a book profit of $15 billion and still have 129 tons of gold.

They captured some of the appreciation in gold value as a realised profit on their books.

Their balance sheet did not change, just their income statement

Very succinctly stated, thank you!