Is it permissible to fulfill the annual vow of sacrifice by slaughtering in poor African countries instead of Egypt, given the high prices and financial inability, while desiring to continue the sacrifice?

If you have vowed to slaughter a fidyah (redemption sacrifice) for your son every year, then this is a vow of obedience that must be fulfilled. If you specified the place of slaughter or the type of animal by word or intention, you are bound by what you designated. If you did not specify a place, it is permissible to slaughter it anywhere. If you designated a place other than the Haram, you are bound by that, unless it involves disobedience [to God]. If the designated place involves veneration of other than God, then it is not permissible to fulfill it there. It is permissible to transfer the vow from a less virtuous place to a more virtuous place, such as the Two Holy Sanctuaries.