Prince Harry will gain nearly $9 million from his great-grandmother when he turns 40 on September 15 — but his brother, Prince William, is less than pleased about the upcoming transaction. “Somehow the idea of Harry walking away with so much money seems wrong to William,” an insider dished. “In William’s opinion, Harry’s done nothing to deserve it and he’s caused nothing but trouble and heartbreak for the royal family since he moved to America.” AsOK! previously reported, William and his wife, Kate Middleton, aren’t on board as Harry, 39, is no longer part of the royal family. “William and Kat…