For bigger and wealthier Commonwealth realms, it is not much of a problem to host the monarch for a week. Howsoever meagre it may be, the nation still has to pay respect to their Queen, host her, and therefore some official money collected from tax payers is spent on the Queen. Are there any advantages for the other nations to still call the British monarch their monarch?
Not to be confused with : Commonwealth of Nations : https://en.wikipedia.org/wiki/Commonwealth_of_Nations