No employer in this state shall be required to pay more for health benefits as a result of the application of this section than would otherwise be required by any prevailing collective bargaining agreement, or other contract, for the provision of health benefits to its employees; provided, that the employer or benefits fund shall pay to the health maintenance organization chosen by each employee or member an amount equal to the lesser of (a) the amount paid on behalf of its other employees or members for health benefits; or (b) the health maintenance organization’s charge for coverage approved by the director pursuant to section 354.435.