A company's valuation is roughly the estimated sum of all its future profits until it shutters or goes bankrupt. Most of those 30 trillion assets are deep into

A company's valuation is roughly the estimated sum of all its future profits until it shutters or goes bankrupt. Most of those 30 trillion assets are deep into the ground, and cannot be turned into profits for free. If you need to spend (say) 2 dollars for every 3 dollars of worth of oil you extract, then the value of the company is already <$10T. The operating expenses can be pretty high. There's also taxes and interest. Also, we don't know what the price of oil will be in 5 or 10 years, so we have to price in that uncertainty too.