Delivery and production speed are two different things. The delivery charge is the cost to post your order to you and the production speed is how quickly your order is processed.
If you choose the express option, your order is prioritised and put to the front of the print queue and is processed and dispatched the same day if ordered before 2pm. The express plus option is very similar to the express option but it covers the extra charge from the courier to deliver your order before 12 the next working day.