The accounts of the Duchy of Cornwall for 2004 - 2005 show that grants total £2,381,000.
This is in its turn made up of three figures £1,242, 000 for the states share of his London office and official residence (in other words the agreed proportion of his expenses that are called official, rather than private) , £1,059, 000 for Official travel by air and rail and £80,000 for Communications.
The is quite a complicated history to this odd sounding term "grant in aid". The Royal family have surrendered the income from the Royal Esates (but not the Duchy of Cornwall), and in return get funding to pay for official costs incurred by thier role in being Head of State. This funding is provided in three ways: (i) a Civil List for The Queen and a Parliamentary Annuity for The Duke of Edinburgh, (ii) Grants-In-Aid, and (iii) costs met directly by Government Departments.
Because of his income from the Cuchy of Cornwall, Prince of Wales does not receive money from the Civil List, but the Grants-In-Aid paid to The Queen’s Household are used to support the official part of his expenses..
There are three Grants-In-Aid paid:
Duchy of Cornwall Income and Expenditure