Good morning ororico.
"So the question is where does the cartel get their silver which allows them to keep suppressing the price so easily as today?"
YES! This is the question of today. We all know that the pm mafia works at the margin. Kind of like "just-in-time" manufacturing. They need to have just enough silver each month to satisfy those who will not be cajoled, bribed, strong armed, into accepting fiat instead of metal. In gold, they have a lot of above ground gold AND companies like Barrick that have a good supply of freshly mined gold entering the market to ward off a default.
It would not suprise me to find out that there are a few silver miners that have a sweetheart deal with the pm mafia to supply silver directly to them and recieve above market prices in exchange of confidentiality. Recall JP Morgan has offered as much as a 20% premium to long clients to accept fiat instead of metal. This probably worked for a few. But it can olny work as long the extra cash allows the client to go "elsewhere" and buy physical. Offtake of physical is the one assurance that the paper hangers will eventually fail.