This demo form demonstrates how you can use Gravity Forms calculations functionality to create a conditional shipping field which only applies when the form total exceeds a specified amount.
For a full walk-through on how you can implement this functionality on your own site, see the Conditional Shipping by Form Total article on GravityWiz.com
Hint: watch the "Shipping"price disappear when the order total exceeds $15.00!
This demo is powered by Gravity Forms v2.7.17.