While her worth has been estimated at anywhere from 2 million to 500 million pounds, no matter how you look at it, the Queen owns an awful lot of real estate. Called the "Crown Estate", in the 1760s, George III surrendered his income from that (or most of it) in exchange for an annual payment from Parliament. 

The Queen's wealth comes from renting and farming operations on the Duchy of Lancaster (which George III did not relinquish), and other private properties as well as receipts from tourist visits to Buckingham Palace. Her son, Charles, Prince of Wales gets income from the Duchy of Cornwall. Both of them, since 1993, have had to pay income tax.

The cost of the Queen in the UK is offset because the Queen surrenders the profits from the Crown Estates (about £220 million a year)  which far outweighs the cost of the Monarchy (which costs about £40 million to maintain). So British subjects make a profit from the entire royal enterprise. No whinging allowed.