[jstanley]

Well then it's not all of the above unless there's more than 375 million kilograms of rhino horns in the world, because all the gold is worth 15 trillion dollars.

Unless that's the case, which seems unlikely, all the gold is still worth more than all the rhino horns.

Also, gold's density is about 19 g/cm^3. I can't easily find a figure for rhino horns, but let's guess about the same as fingernails, horse's hooves, etc., which is about 1.25 g/cm^3. Gold is 15x denser, so at the prices you've shown, gold is still worth more than rhino horns per unit volume.

[usuehfjfi]

Price per volume is not used because volume changes with altitude. This is the reason planes measure fuel by weight. And scientists measure gases by weight.

Because weight is the best way to compare things.

[a_c_s]

"x is worth more than gold" means the price per unit of weight of x is greater than that of gold.

What are you trying to achieve by arguing that a common turn of phrase doesn't mean what everyone else thinks it means?