Coated Blades mana cost is paid four times instead of once when you make Puncture a spender with the Penumbral Ambush node and take the Stay of Execution node to make it charged.
You pay the skill mana cost and one instance of the Coated Blades cost upon starting a charge, but then the cost is paid three additional times when the charge is released. It seems to me that the releasing of the skill counts as a ‘use’ of the skill as far as Coated Blades is concerned, and it counts as three uses since there are three Punctures going off (yours and your two mirages’).
I’ve created a video to quickly showcase this cornercase interaction.
