I know very little on this, but here goes.
So this is where we get into the murky waters of lies, damned lies and statistics. Royalists will tell you they bring nothing but sunshine and joy to the whole world at a cost to nobody, abolitionists will tell you they cost the earth.
The royals are paid out of UK treasury coffers in the form of a sovereign grant (which replaced the civil list). The amount of that grant is determined as a percentage of the profit from The Crown Estate which is paid directly to the UK treasury in the first place. The Crown Estate is owned by the sovereign in right of the Crown and is not the personal portfolio of the Queen. Whether you believe that the Sovereign is entitled to that ownership is something you can determine based on your own outlook.
The sum that Jo referred to as the cost to Australia is in fact the cost of being part of the commonwealth, which these days has nothing to do with having the Queen as monarch and is simply a cooperative of nations. This "club" seeks to enhance the lives of its citizens and share expertise that is of mutual benefit.
If we talk about the cost of the Royal family visiting a host nation on their invitation, yes that cost is borne by the host nation, but that is in no way different to any other dignatory. In the article I read, apparently the cost of Oprah Winfrey visiting Australia cost its taxpayers more than the Queen's visit. In the same way when the Pope visited Canada there was a significant cost to Canadian taxpayers as a result of that trip.
It's way too boring to go into too much detail, but if you'd like some links for reading, I'm more than happy to pass some on.
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