There's hidden cost associated with offering a paid membership for "privileged" users, in that it affects the overall perception of the product. Many non-paying

There's hidden cost associated with offering a paid membership for "privileged" users, in that it affects the overall perception of the product. Many non-paying users would feel negatively about it, and start looking for alternatives. As a result, the membership fee has to cover (1 + lost users) advertisement revenue.