The primary sector is only a very small part of the economy though. Prices for raw materials are low because it's easy to mine etc vast quantities nowadays and there is a lot of competition in global commodities. Most minerals are found in a LOT of places all over the world.
Land. Total value of it is about 25 trillion in the US alone I believe. If I'm not wrong, globally stock markets are around 100 trillion (and that will include a lot of assets in the form of land).
25 trillion is just 1 year worth of GDP. With interest rates of 5%, that's only further evidence for my point.
Edit: as an exercise, consider the land value of a typical office, and compare to the annual income of the part of the company based there, and the personal income of the employees who work there.
