How Much Does €640,000 of Gold Weigh?

For very long periods of time, yes, gold is an excellent store of value.

Before 1971, the U.S. was on the gold standard. This meant that the price of gold was fixed at $35 per troy ounce. Since that time however, the price of gold has increased by about 8% per year, more than twice the rate of inflation, and much more than bank interest rates.

This doesn't mean that there haven't been ups and downs. Between 1980–2000, the price of gold declined considerably.

However, with governments printing more and more money due to the Covid-19 and pension crises, it seems likely that gold will continue to hold its value well.

According to Wikipedia, there were 201,296 metric tons of gold above ground as of 2020.

With a current price of $2,324 per troy ounce, this means that all the gold in the world is worth $15.0 trillion.

In the year 2022, the world mined about 3,300 metric tons of gold, adding about 1.6% to the world supply. At current prices, this gold would be worth $247 billion.