TarunKumar Dynamic Delivery Charges is built to work in two ways:
Without Google Distance Matrix API.
It will calculate the distance from one point to another with an algorithm inbuilt on Foodomaa itself. No 3rd party integration. So no additional cost of any kind.
(Not very accurate)
With Google Distance Matrix API.
It will fetch driving distance from one point to another provided by Google. Google cost is involved here. Will only work when Google Distance Matrix API is enabled on the Admin Dashboard.
Personally, I have found GDMA doesn't use much of your cost, the cost comes from when the customer keeps on moving their finger on the Map that is shown on the Order Tracking page. (it can be disabled from Admin Settings as well)