Question : How does this web site manage to pull data from many different sources?

How does this web site manage to pull data from many different sources?

http://www.bizbuysell.com

Is it likely that it is plugging into various premium web services or is this something that can be developed freely by anyone who has the time and skills?

Answer : How does this web site manage to pull data from many different sources?

Note that http://www.bizbuysell.com/ is not a price comparison site,  buying and selling businesses is their business and they are part of a large real estate firm.

As for a price comparison site, I doubt that any of the businesses 'publish' price data in any way but what you can find on their web sites.  Most are not interested in being compared unless they are doing the comparing.  I think you will find that most of the 'legitimate' price comparison sites have their own 'web bots' that search the web for the products and prices they want to compare.  They probably have automated Google and Yahoo searches too.  Why do all the work yourself?

At the bottom of their main page, NexTag describes themselves as "the Search Engine for Shoppers™".  Bizrate is a similar site.

Here is more info about price comparison sites: http://en.wikipedia.org/wiki/Price_comparison_service