That may be true in Duchess of Alba case, but the Liechtenstein royal is not hurting on cashflow. The LGT bank which is owned 100% by the family, makes around 300 million CHF every year. Here is a news link. https://www.lgt.com/en/news/lgt-reports-good-results-and-strong-net-asset-inflows-in-2020/
The family also owns winery, real estate, forestry, and wind farms. All of these businesses produce cash flow steadily. A New York Times article estimates that Prince Hans Adam spent 18 million a year on art. Here is the NYT article link.
https://www.nytimes.com/2004/06/28/arts/museum-in-a-vienna-palace-fitted-out-by-a-prince.html
The family also owns winery, real estate, forestry, and wind farms. All of these businesses produce cash flow steadily. A New York Times article estimates that Prince Hans Adam spent 18 million a year on art. Here is the NYT article link.
https://www.nytimes.com/2004/06/28/arts/museum-in-a-vienna-palace-fitted-out-by-a-prince.html
The Fürst and his son the Erbprinz receive no income from the State but all their expenses are met. So their accomodation, representation, transportation, security, facilities, utilities and staff are paid for. The portrayal is "wow, that head of state does it all for free" but that is factually nonsense.
The billions of wealth attributed to the Fürst in popular media are also not the personal wealth but the fortune of the House, with the large art collection as main element.
To paraphrase the late Duchess of Alba: "Rich? Rich? I can not go to the supermarket with a Rembrandt under my arm" meaning that a family can be wealthy in assets but not necessarily in cashflow. The family Von und Zu Liechtenstein is quite extended and almost all of them work for their living. I can not think of any Liechtenstein Prince rolling their Euros or Swiss Francs in Monte-Carlo or Marbella.