It's based on the C30 series (I believe), which are in the US $25,000 range for second generation:
http://www.automotoportal.com/article/volvo-announces-pricing-of-the-new-c30So add in the extra equipment and engineering, and I would estimate at least US $35,000. Similar opinions exist here:
http://blogs.cars.com/kickingtires/2007/09/volvo-plug-in.html#moreThe press is a little unclear, but I strongly believe this exists only as a prototype C30 alteration. Being a concept vehicle, and believing that Volvo takes 3-5 years to follow through, this vehicle could debut as early as 2011. Dollars to donuts, though, Volvo will release several significantly increased efficiency vehicles before 2015.