[Renall]

I imagine it's mostly just a matter of reality not matching up to expectations.

Ten tons of gold is a very large quantity. It's also an extremely valuable quantity. So you assume it must take a ton of physical space. But gold is very dense, so it doesn't take up as much as you'd figure. And Kinzo's gold is monetary gold (presumably), which is bullion, which tends to be 99% pure metal (gold used in jewelry and whatnot would not be this pure).

By contrast, Fort Knox's bullion reserve has about 4,500 metric tons and the Federal Reserve Bank of New York has about 7,000. Combined, that's about 8% of all gold that has ever been mined.

Also a random fun fact, but most gold bullion ingots are very small. Kinzo's are repeatedly portayed as appearing somewhat large, especially in the anime and manga, but a 1kg gold bar is fairly small (it would basically fit on your open hand). The size of bars most people imagine for Kinzo's stash would actually be a more appropriate size for silver, which is less dense.

EDIT: Which isn't to say the RSI or whoever couldn't have melted it down and intentionally recast it in 10-100kg bars for whatever reason, since that is apparently what happened with it. A 100kg gold bar would be decently big, but I can't imagine Rosa trying to carry one for long while running.

EDIT EDIT: Also by a conservative estimate, if Kinzo's bars were 10kg, each would be worth a quarter of a million dollars or so. Although I think the price of gold was (relatively) higher in the mid-80s, it's gone down a little recently.

EDIT EDIT EDIT: Ha ha, Kinzo doesn't even have 10 tons of gold, or Battler is lowballing its value in End. He suggests it's 20 billion Yen. On 10/03/1986 the value of gold was $430/oz (yes, they recorded this that precisely), which is about 72,463.6 Yen at 1986 exchange rates. That's 276,000.64 oz, which is only 8.625 tons (or 7.654 metric tons).