To add to all of this, japan-guide.com has fantastic resources on getting around Japan, including time, pricing, and rail pass information between cities. The rail pass mentioned by abmj-jr is here: http://www.japan-guide.com/e/e2361_k...hiroshima.html

It seems like Kyoto-Hiroshima would be north of 20,000 yen roundtrip and the rail pass is only 13,000 yen, plus you get to use it to/from KIX and to/from Osaka/Kyoto/anywhere else in the region.