For retail ecommerce shopping engine optimization can be a real challenge. We are all trying to hit our ROI and revenue targets so being in a competitive pricing environment isn't always the best vehicle.
Fear not their are some ways to improve your shopping engine rankings and performance.
1 - Enhance and optimize your data feed
Whether you push the feed or you have a partner scrape your site for your data feed, look at what is being sent to the engines and enhance it where necessary to ensure that you are being categorized correctly, your product description is clear/enticing, your images look good, the language being used is what a consumer would actually type in (especially important if your merchants write your product descriptions) and/or you are pushing products that you actually have stock in. You can think of your data feed as being able to control organic search listings within the shopping engines themselves, therefore monitor and adjust as needed to reap better performance.
2 - Bid for higher placement
Follow the same strategy and tactics as your paid search campaign, although you might have to increase your ROI tolerance due to the competitive shopping environment.
3 - Insert your logo into your feed.
Most engines charge a premium for this but it helps the listing stand out and improves consumer confidence.
Final thought on feeds: It normally doesn't matter if you push the feed directly out of your site's backend or you have the site scraped as long as you are monitoring and actively optimizing the data feed.