perth mint has run out of silver bars, page-65

In that interview, Ross Hansen says what I've been saying and that is that there is no problem getting supplies of gold or silver in the wholesale markets (we refine 300t of gold a year) and that delays in retail coins and bars are a production capacity issue.

As to the supply/demand situation, it is quite complex in the case of silver with it being a by product of mining of other metals plus the industrial and monetary demand aspects, so I don't think it is as straighforward as Ross Hansen says.