In Buffett's most recent annual letter, he writes an interesting passage on the value of gold relative to other assets. He writes that if all of the gold in the world were combined into a solid cube, it would fit roughly in the infield of a baseball diamond and be worth $9.6T. He goes on to write that this is approximately equivalent to the value of all of the farmland in the US and 16 Exxon Mobils combined (plus another $1T of cash).
It's an interesting thought experiment, since few actually have $9.6T to spend, but here are some other big ticket items to compare to the price of Gold:
Global Oil Reserves: 1.3T barrels x ~$110 per barrel = $143T
Global Equities Market Capitalization: ~$55T
Total US Credit Market: $37.8T
US Real Estate Market: $18T
US Treasury Market: $10T