Pharmacies providing prescription drugs under this Article shall be reimbursed at a rate which shall include a professional dispensing fee as determined by the Illinois Department, plus the current acquisition cost of the prescription drug dispensed. The Illinois Department shall update its information on the acquisition costs of all prescription drugs no less frequently than every 30 days. However, the Illinois Department may set the rate of reimbursement for the acquisition cost, by rule, at a percentage of the current average wholesale acquisition cost.