I have seen some comparison sites that a user asks for a specific product (with some specifications) and the site returns prices from several suppliers with short description , actual price , and a link in order to proceed with buying of it . That is real value to the end user . I predict that have high conversion rates . I am talking about sites like kelkoo and some other smaller. But how do they built such a comparison engine? I mean from the technical side . I started once to build an engine for booking flights and i reached the point where i constructed url queries (url queries to merchant sites ) showing to the user the links where he could find more info like , price , descr etc. Really very hard work trying to understand how the merchant works , what are the parameters passing , deep linking and so on. But these comparison sites are far more better . They show actual price + descr + link to book .