Let's say I bought a 100-ounce gold bar in 1965, when gold was $35/oz, for a total price of $3500. Let's say I sold it today at $4700/oz, for a total price of $470,000. That gives me a gain of $466,500.
And let's say that I regret it. I decide that I really want to hold some gold, so I take the $470,000 and buy another 100-ounce gold bar.
The situation was that I had a gold bar worth $470,000 with a taxable basis of $3500. Now the situation is that I have a gold bar worth $470,000 with a taxable basis of $470,000, and I owe the IRS taxes on $466,500 of capital gains.
TL;DR: Selling and re-buying the same asset gives you the accumulated gains, and resets the price basis.
They had gold worth X to the market but X minus 11 billion on paper. So when France accounted for its gold in euro terms they would say they have X minus 11 billion Euros worth of gold.
Now they still have the same amount of gold but they "realized" a gain of 11 billion. They don't have that much cash left after the repurchase but now they say they have X Euros worth of gold which is 11 billion more than before.
So no they didn't make a profit from this as gold is higher on both sides of the Atlantic than last time they did their accounting updates.
