The commission shall have continuing supervisory control over the terms and conditions of contracts and arrangements as described in section 2102 (relating to approval of contracts with affiliated interests) so far as necessary to protect and promote the public interest. The commission shall have the same jurisdiction over the modifications or amendment of contracts or arrangements as it has over such original contracts and arrangements. The fact that the commission shall have approved entry into such contracts or arrangements shall not preclude disallowance or disapproval of payments made pursuant thereto, if upon actual experience under such contract or arrangement it appears that the payments provided for or made were or are unreasonable.