Effective Free Shipping Messaging

Most sites promote free shipping offer on cart page like this (red arrow in screenshot below)–

This is a 6, on a scale of 10.  This is how Amazon.com promotes their free shipping–

In both cases the effective shipping price is $0.  But Amazon’s approach is more effective because they have an action element.  Amazon first shows the $6.98 shipping fee, and then waives it for me.  I’d give this tactic a 9, on a scale of 10.