Shock in prize difference of in store and the app.

Last night I'm on the road, stopped at my favorite restaurant for a quick take away. Ordered the exact same thing I usually do on Mr D app. But was confused of why I paid less for the food (I'm aware of the delivery fee and driver tip). Quickly went on the app, while I was in the restaurant. With a shock I saw that the food prizes are not the same. Mr D is more expensive. Then on top of our order you have to pay delivery fee and a driver tip. I was shocked. Will never use Mr D again, this is day light *******. From now on I will call the restaurant and collect myself.