A set of replacement doors at Windsor Castle in Britain cost £1.2m (€1.36m), new royal accounts show.
The 20 bespoke doors were installed on the East Terrace after the previous set suffered severe wood rot and decay.
Figures show the British monarchy also spent £1m (€1.13m) on ceiling inspections and £1.5m (€1.7m) on food and drink hospitality within the royal households.
Meanwhile, travel expenses for the royals topped £4.5m (€5.11m) - including a €175,000 trip to Italy, Romania and Austria made by Prince Charles and Camilla in April.
Other costly trips included Prince William and Kate Middleton's state visit to India and Bhutan (€111,067), and Prince Andrew's trip to Mozambique and Botswana (€61,386).
The Royal Train was also expensive, with £288,697 (€328,186) spent on just 14 trips.
One of those visits was made by Prince Philip to an anniversary dinner in Devon, which cost £18,690 (€21,246).
A royal source said: "We believe that, though it's not the cheapest way to travel, it does represent many of the features that we look for in terms of safety, security, not causing disruption to lots of other people - convenience - environmental aspects it's strong on as well."
The annual accounts show Queen Elizabeth II's expenditure was £41.9m (€47.6m) last year.
It came as the profits of her estate jumped by 8% to £328.8m (€373m), while Prince Charles' private income was £20.7m (€23.5m).
Alan Reid, the Keeper of the Privy Purse, said the Sovereign Grant paid to Queen Elizabeth II equated to 65p (73c) per person in the UK.
