The financial aspects of having a modern monarchy

In the thread about the fading of the Church of England, someone compared the costs of the state religion (in forms like the lack of property taxes other entities would pay for the same land, and tax funding of programs instigated and/or run by the church) with the costs of keeping the royal family royal.

I don't get it. What are the costs? Every other rich family I know of stays rich because money makes it easy for them keep & get more money. What additional money is given to this family on top of the usual? Are they protected from extreme loss that can befall other rich families if they act foolishly enough? If there is actual income/payment involved, could this not be defunded even while keeping the monarchy a monarchy? Are we talking about indirect advantages like not paying property tax? And if so, how much is that anyway, given that some royal properties are used for government purposes which might not be taxed anyway if they were retained as government properties unaffiliated with monarchy? And how does it compare with the income from monarchy-related tourism?