Funding for the young royals leapt more than 40% in the year the Duchess of Sussex joined the family.
Clarence House released its annual accounts, which includes funding for the Duke and Duchess of Cambridge and Duke of Sussex.
In 2017-2018, the total went up 41% from £3.5 million to £5 million.
Harry and Meghan announced their engagement in November last year and married on May 19.
William and Kate had their third child Prince Louis on April 23.
Charles's principal private secretary Clive Alderton said the year was one of "celebration, commemoration and change" and included "moments of great joy" for the Royal Family.
He added: "The Duke and Duchess of Sussex became engaged, their wedding itself seemed to me a day when not just the sun shone but Britain itself shone - and right round the world.
"The Duke and Duchess of Cambridge announced that they were expecting another child and the Prince of Wales's third grandchild Prince Louis was born in April.
"The Duchess of Cornwall celebrated her 70th birthday and as she has been saying to everyone, the Prince of Wales is about to catch her up in November this year when he celebrates his own 70th birthday."
Funding for William, Kate and Harry's "activities" are listed under "Other Costs" - which also includes capital expenditure and transfer to reserves, but there is no further breakdown or detail.
The figures show Charles's annual income from his hereditary estate the Duchy of Cornwall has increased by 5% to £21.7 million.
His tax bill has increased 2% from £4,757,000 to £4,854,000 in 2017-2018.
As heir to the throne, Charles is entitled to the surplus generated by the Duchy's vast portfolio of lands, buildings and financial investments - which includes the Oval cricket ground and 67,000 acres of Dartmoor.
This year, the Prince and the Duchess of Cornwall carried out 619 engagements in 44 counties of the UK, plus official visits overseas to 15 countries.
The cost of Clarence House's official travel by air and rail was £1 million in 2017-2018.
Charles travelled to the Caribbean in the aftermath of two hurricanes last year.
Other overseas trips by the Prince and the Duchess of Cornwall included India, Malaysia, Brunei and Singapore.
The Prince also receives taxpayer funding from the Sovereign Grant, a figure which fell from £1.3 million to £1.2 million.
Charles uses his Duchy income to pay for his official duties, his London office and charitable work.
Charles pays income tax voluntarily on the surplus of the Duchy of Cornwall, applying normal income tax rules and at the 45% rate, and pays income tax on all other income and capital gains tax like any private individual.
The annual review also showed that greenhouse gas emissions from the Prince's household decreased by 9%, with all electricity used by the household coming from renewable sources.