Does exchanging gold between two sisters as a concession and change, not a sale, fall under the category of usury?

It is not permissible to exchange gold for gold except if it is like for like, hand to hand, due to the authentic Ahadith reported in this regard. The lack of equivalence is not excused by the fact that the two parties exchanging are sisters, for each has an independent financial responsibility, and they are like strangers in transactions.