When it comes to deploying outdoor signs the price of a sign is the least of your worries when it comes to TCO. It's more about how much does it cost to deploy and how much does it cost to manage the signs. Digital signs also give you the ability to update information more often.
Given the positive feedback from the end customer and Mercury Innovation (http://www.mercuryinnovation.com.au/) that took our platform and built the traffic sign (we're not the ones selling the end product) I'd say that TCO is in favor of e-paper traffic signs.
How many employees could be hired changing the physical road signs given the price difference?