The Prince of Wales clocked up a £20,000 bill to travel by train from London to Port Talbot , royal accounts have shown.
The next in line to the throne visited the steel town to meet with youth groups and an arts and activity project for older people.
But the cost of his travel getting to Wales has emerged in royal accounts that were released on Tuesday.
They also show that the renovation of the Duke and Duchess of Sussex's Frogmore Cottage in Windsor cost taxpayers' £2.4 million.
Harry and Meghan's country residence, close to Windsor Castle, underwent major work to turn five properties back into a single home for the couple and their baby son Archie - with all fittings and fixtures privately paid for by the duke and duchess.
It is likely they installed a luxury kitchen and bathroom and it has reportedly been fitted out with a mother-and-baby yoga room, complete with a "floating" or sprung wooden floor that replaced Victorian floorboards.
Accounts for the Sovereign Grant, which funds the Queen and her household's official expenses, show the monarchy cost the taxpayer £67 million during 2018-19 - an increase of almost £20 million on the previous financial year.
Despite the high cost of some journeys, royal sources insisted the royal train offers value for money when security is taken into account alongside the types of engagements, the accommodation on board and the cost of alternatives like planes or helicopters.
Graham Smith, from the Republic campaign group, has criticised the increase in overall expenditure by the royals.
"This year's increases are outrageous at a time of widespread spending cuts. If even one school or hospital is facing cuts we cannot justify spending a penny on the royals. Yet with all public services under intense financial pressure we throw £2.4 million at a new house for Harry," he told the Sun.
