Prices of food going up due to temporary disruptions (usually weather related, or government related (the stupid policy of burning corn for fuel)) is usually temporary as bubbles could burst as soon as the next harvest anywhere in the world.
Gold and silver are different in that they are hard to find, and it sometimes takes years to gain required permits. Also, the whole world is still under-invested in the precious metals, including central banks. When everybody from the bus boy to the bus boy’s grandmother is invested in gold and silver, I will say there is a definite bubble.
Go back to the early 80’s and look at the price of gold and silver then.
The fundamentals have little to do with bubbles. It is all about how much money is chasing something... and then one day, the big money decides to fleece the little players and they sell.