Several conditions, like cart subtotal, product attributes, customer groups, shipping methods, etc., can be set up to trigger or activate extra fees using Magento 2 Extra Fee Extension. For example, you can set the condition to activate the extra fees once the shopping cart reaches a certain amount.

Read this configuration guide on How to Configure Extra Fee Extension in Magento 2.

1. How to Add Extra Fee to Magento 2 Orders and Checkout?.