My imagination?
It's no longer a matter of supply and demand, as evidenced by the fact that there has been no reduction of supply, and relatively minor increases in demand.
There are a few important factors that you do not address.
One big factor is flexibility of demand. When demand is inflexible (like oil or food) then even small shortages can result in large price swings.
Substitutes
If there is not good substitute product, then again small shortages can have a big impact.
Fear and emotional factors.
When people are afraid of shortages of an important product with no substitutes, they tend to hoard and increase a small shortage
Globalization
the "miracle" of a highly globalized economy means that it is easy to move money around and buy resources where ever they may be. Just to give an example, if the Chinese were inclined to do so, they would have enough cash money to largely corner any commodity market they choose with out using any leverage.
