class DummyClass extends ShippingType
* Calculate the price as you need it. This example will return the price as defined
* in your shipping rate. This is how "shipping by price" does get calculated.
public function shippingCosts(): string
* As an second example. This is how we do calculate the "price per item"
// $price = $this->makeAmountSaveable($this->rate->price);
// return $this->makeAmountHuman($price * $this->itemCount);