How much of free do I have to give away until I start to make money?

If I have said it once I have said it a million times, cash flow is the life blood of any business. But if that is true, how can you make money by giving things away? Google is free to use, but it makes billions of dollars in revenue.  This is an issue I have been thinking about for months and how it relates to the RPG industry.  Webcomics have tackled this issue and seem to have it under some control. Take a look at PvP, Sheldon, Evil Inc., Starslip and Girls with Slingshots to see successful business that make money by giving away their main product for free.  Why can you not find any “successful” RPG companies using this model? Is it because our niche is too niche?  How much free do I have to give away until I start to make money? What do you think. Let me hear your opinions on this topic.  Talk to you later...