Given Nissan's previous stall tactics, I doubt we'll see a price until someone needs to pay to have it replaced for degradation or failure (passes 8 year/100K mile capacity and defects warranty) or an unlikely accident that severely damages the battery but not the rest of the car sufficiently to total it.
For the 24 kWh packs, we were originally promised a price in Spring (IIRC) of 2013 and didn't get one. We instead got http://www.mynissanleaf.com/viewtopic.php?t=13331 on the very last day of that season. ThankyouOB kept err... asking Andy Palmer when he'd tell us the price. Hopefully http://www.mynissanleaf.com/search.php?st=0&sk=t&sd=d&sr=posts&keywords=andy&author=thankyouob works.
After going silent for a year, we finally got a price http://www.mynissanleaf.com/viewtopic.php?t=17168.
In the Andy Palmer video from 2012 at http://www.mynissanleaf.com/viewtopic.php?t=10257, they claimed they at the time didn't envision the customer having to pay for the battery, hence no price at the time.
I couldn't find it via a quick search at https://parts.nissanusa.com/. I suspect a call or visit to a Nissan parts counter will turn up no price.