Free is good. Free is honest.

You build something (product) and then tell everyone about it (marketing) and usually the latter is what takes a larger amount of energy. It is arguably the hardest thing in the world to tell somebody else what to do and it is only more difficult for a startup when it is something new that they have to offer.

Typical consumable goods companies spend an enormous amount of money in informing the masses about what they produce and why it is the best option. And there is good reason to believe that their mass communication methods are highly inefficient. On the other hand some companies allow (their potential paying customers) to use their product for some time for free. Instead of viewing this as the opposite of revenue (not charging for what you intend to), this expenditure should be viewed as a replacement to the advertisements or ‘gentle yet expensive nudges’ that has traditionally been spent in marketing all products. 

Like marketing expect this to be a long term investment and don’t get disheartened if you don’t see any revenue coming in soon after you announce your product. Unlike traditional marketing though, it will be far more ‘honest’ !