PMs, Russia and China. Price manipulation. Am I wrong here?

I am no expert in pms but I do hold a modest amount for a rainy day.
I have a thought on why the price of pms always seem to be controlled by tptb.
I take it that the big players also hold large amounts of silver, as well as gold, which they have been constantly increasing their holdings over the past few years?
Now, surely, it is in the interests of tptb to keep the price of pms down or China, Russia, etc. would amass great wealth should pms skyrocket.
Seems to make perfect sense to me or am I missing something here?