500 Million is not rich. It is a small average neighborhood in London.
The Sovereign actually doesn't need wealth, and hasn't since Plato's Republic. Possibly you have her confused with rich individuals in the upper classes, like Trump, Buffet or Gates. She better than that.
She is given everyting she needs to do her job as sovereign by her subjects. The assets of the crown are owned by the commonwealth, not her. It's not like she's going to sell Buckingham Palace and escape to the Caribbean with the money.
In essence she is a well paid public servant with an endless reality TV acting job, having 24 hour lifetime coverage.
What she does own privately is a hot stamp collection and a bunch of race horses, her hobbies. That is about 250 mil worth. Cut the poor lady some slack.
She is doing it for the duty, not for the lols or cash prizes.

The steeemy Queen of Canada.