My conversion rates vary considerably, depending upon the time of year. At Christmas time it can be 20% to 25%. In the summer it dips real low to about 2%. The average is probably 10%.
Be careful with using any Amazon plugins that use the Amazon product descriptions and user reviews verbatim. That is still the kiss of death for an Amazon site due to Google's duplicate content filters. You need to either write the descriptions manually or scramble them to get past the filters.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin