How to : Nextag and such other dynamic data pulling website

Question

Yesterday, I came across Nextag which is a website for comparing prices of various products from different retailers. Is this site automated?

Can the process of data pulling from various sites can be automated for comparison with each other. I tried understanding a hell lot, but could not realize this fact and now think that they ought to be manually managed because on every other retailer site, the product name was different and it was very hard to recognize a similarity for a specific product.

I have made such a system in which one can add a product and then add the respective retailers and their pricess. Every thing is manual in here. Today, I will be entering the data into the system, but thought it would be better to know if there is a way to automate this thing. Or I am going the right way as there can't be an automation for such system, because the data has no similarities.