If the old ones are anything to gauge by, it will not be cheap. personally, while I love the idea behind the technology, I'm not sure that it is all that usable in watches, especially when you consider that with todays kinetics and solar watches extended battery life (which is the principal benefit behind e-paper) are easily achieved - often beyond the usable life of the watch itself.
In watches, screens are so small, and so little information is displayed (and what is is mostly info to be read at a glance) that the benefits of deep color contrast which are so evident on e-paper book readers, are also lost.
What I would really love to see if digital watches with full color AMOLED screens. those give you resolution, high contrast, low power consumption, toughness and long life.