Helmets...new or used??? Help!

Newbie here...

I'm buying my first bike and the guy selling it is offering a 2000
Arai helmet (on of the top-of-the-line ones) for $300 as part of the
deal. New, they're about $900 I think. He said he droped it from the
seat once, but I've seen it and it hardly left a mark.

So the question is, should I go for it or do I need to get a new one?
I'm already over budget...

Thanks!!!