How much does Walmart charge for a vial of insulin?

Could you please clarify for me, what is the current pricing structure that Walmart employs for the purchase of a single vial of insulin? I'm particularly interested in understanding if there are any variations in cost based on the type or brand of insulin being sold, as well as any potential discounts or promotions that may be available to customers. It would be greatly appreciated if you could provide me with a concise and accurate overview of Walmart's pricing policy in this regard.