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How are people coming in to the pages - via search?
Are the keywords reasonable ones for someone who is wanting to BUY what you are SELLING, or are they overly broad, or more informational?
You always always always have to think about user intent.
It sounds like you are attracting tire kickers and/or information seekers, and not buyers.
Product/Category pages 65% (avg 75%) bounce, that's where you should concentrate in my view and figure out why most of the visitors leave early. Try to bring it down to less than 40%.