Or, for that matter, why does any other software product that is bought and sold online cost money? You can buy all kinds of software without ever leaving your chair, and those applications are (like news), really just bits and bytes – easily and freely replicable ad infinitum.
As far as I can tell, the important difference between software and news is that software tends to have perpetual utility. In other words, I bought my copy of Vista years ago, and it’s still useful to me today. The copy of the New York Times that I bought last week is already getting pretty stale.
If you want to charge money for your news, and I think you should, then you have to provide some lasting value to your offering; that may come in the form of access to well-maintained databases, or it may be a collection of member discounts (why do people becom Costco members?).
Maybe the way that people interact with your content is different? Maybe people who pay get a better browsing experience? Maybe they get desktop software?
Food for thought.