The best way to find out could be via “teasers”, such as a free newsletter with snippets of information that people have to subscribe to to get the full story. Also free trial periods might work, or say 3 free articles a month. An old tactic is to offer three levels of subscription: say platinum, premium, and basic. Make the platinum so expensive that nobody buys it, and the basic so limited that nobody wants that either, and people will be more motivated to buy the premium subscription. They’ll get the impression they are getting both good value and good content, even though the other subscription levels were never intended for sale anyway.