"We will see if Willem-Alexander must also make concessions on payments next year, " Mr. Matthijs said.

WSJ: An Austere Coronation for New Dutch King

By contrast, the total cost of salaries and material expenses for the Dutch monarchy increased 4.5%, according to Mr. Matthijs' calculations.

WSJ: An Austere Coronation for New Dutch King

"The Netherlands are now, next to the Scandinavian countries, the only country where the royal family does not have to compromise" on expenses, said Herman Matthijs, a professor at the University of Ghent who has studied the budget costs of Europe's royal families.

WSJ: An Austere Coronation for New Dutch King