William and Harry inherited over $40 million from Diana's estate ($28 million from her divorce settlement with the remainder from the Fermoy and Spencer inheritances). At this point, the income is payable without restriction until they are 30, at which time they will start to receive outright distributions of the principal of the trust. Most trusts pay out a pretty conservative percentage in order to maximize growth for the future. As such, it is likely they are each receiving about $500,000 annually.
The Queen Mother transferred her personal fortune ($10 million) into an irrevocable trust for her great-grandchildren years before she died. Harry receives a small income from it, while receiving a sizable income from his trust set-up by Earl Spencer ($5 million). Once The Queen dies, the irrevocable trust automatically terminates, and the remaining principal is distributed to Anne, Andrew and Edward in equal shares.
Charles gets nothing because he will inherit the vast majority of his mother's personal fortune as the new Sovereign. William gets very little because he will become The Duke of Cornwall and have a sizable income from the duchy. Harry is provided for by his Spencer trust and his mother's legacy.