How to create a fee that'll be available for a certain subtotal only?
Fees can be set to be visible once customers add some items totaling in a specific amount to the cart, or vice versa: hide the fee as soon as customers reach a certain subtotal. To do that while creating your fee at Stores → Configuration → Amasty Extensions → Extra Fee → Fees → Add New Fee, please navigate to the Conditions tab, add Subtotal condition and define its value. In this example, the fee is visible for orders with subtotal less than 100:
Let's test the fee after saving it. It's displayed for orders with $45 subtotal:
But disappears as soon as subtotal reaches the defined level: