Is it permissible to compensate the wife who was not visited for a week during an upcoming trip, in exchange for spending the vacation week with the other wife, knowing that visiting the first wife is financially costly?

A husband must be just among his wives in the division of time, by spending a night, or two, or three with each wife. He is not permitted to spend more than that with one of them without the consent of the others. If the two wives are in distant countries, he may divide his time between them on a weekly or monthly basis, depending on what allows him to reconcile between them and taking into account the proximity or distance of the countries, unless one of them refuses to come to him if she is able to do so. Therefore, there is no harm in your staying with the new wife for a week, provided that the old wife is compensated for her right.