Kind of like how Door Dash and others show free delivery, or $1.99 delivery. Then when you checkout, you have a "service" charge as well as a request to tip (i.e. actually pay because we aren't paying them anything) the delivery driver.
Kind of what MercadoLivre does. The seller pay extra to offer "free shipping", the product is listed as free shipping but depending on what it will cost MercadoLivre they add a surcharge during checkout.