Sounds like a bargain! I can't remember exactly what we paid for the tour aspect, but I recall that the whole 4 days including flights from Heathrow and a night in a 'top russian hotel' in Kiev wasn't much short of £700. Well, I say 'tour', but it was just two of us and we had the guide take us wherever we wanted to go for two whole days so that we could spend as long as we wanted getting our photos.
Our initial contact was Dylan at Lupine Travel, but it doesn't matter which agent you book with, you'll ultimately be guests of Sergei who runs the only tour operation that's allowed inside the zone of alienation. Can't remember the name of his company right now ...
My mate is going over again this easter, but taking his own food along.
See
http://www.muppix.net/chernobyl for the pics.