What is the ruling on commercial transactions between two neighbors who exchange goods and settle accounts and financial differences weekly?

What you have mentioned is a form of set-off between two debts that are of the same type of money but differ in amount. As long as this is done by mutual consent, there is no harm in it. Set-off (muqāṣṣah) is the cancellation of a debt owed by one person to their debtor, in exchange for a debt owed by that person to their debtor.