Hi,
Been on amazon for ages, now providing services for eCommerce starters to successfully promote their positions on different selling platforms. I've got what you need - a group of Amazon customers who will do your task, including but not limited to: writing comments, reviews and putting stars for your product line as verified purchasers or as thrid-parties. A5$ survey is fine, but you might need more to success. A good rating as a seller and the best rating for your product line - are other two steps.