Priority delivery fee is a scam on all services. If your order is sitting a while, it's generally because the $ to mile ratio is too low. A $2/mi order is considered a base line for most drivers. Orders will start with a low base pay of $2-$2.75 + tip. If drivers keep declining to pick up your order, it'll get batched with another order. Priority delivery fee goes to the delivery service, so you might as well put that towards the tip instead to get it picked up faster by a driver.