Comments like these make me laugh. You realize they put all their own assets in Trust, and draw income from them, right?
They have some many lands in trust used for the public now, and many generate income from tourism. And they get that.
So the UK government took over their stuff through trusts, and they now get to still use it and get some of the income from it. But much goes to the people. So they actually are a net positive.
WikipediaThe finances of the British royal family come from a number of sources. The British government supports the monarch and some other members of the House of Windsor financially by means of the Sovereign Grant, a percentage of the annual profits of the Crown Estate which is intended to meet the costs of the sovereign's official expenditures. This includes the costs of the upkeep of the various royal residences, staffing, travel and state visits, public engagements, and official entertainment. Other sources of income include revenues from the Duchies of Lancaster and Cornwall, a parliamentary annuity, and income from private investments. The Keeper of the Privy Purse is Head of the Privy Purse and Treasurer's Office and has overall responsibility for the management of the sovereign's financial affairs.
https://en.wikipedia.org/wiki/Finances_of_the_British_royal_family