Believe it or not, nobody wants something for nothing. If you look at any kind of event or class, virtual or real, no matter how much interest people have in it, if you don't charge money people stay away in droves. Seems counter intuitive, but almost any kind of event where tickets or reservations are given out free-of-charge to potential attendees typically will have high no-show rates… on the order of 35% or more. In comparison, when people have to pay real money, even if it's a relatively modest amount, no-show rates drop to 5% or less.
Another thing that people understand is that "you get what you pay for", especially in business or any kind of competitive arena. People commonly mistakenly think that the cheaper you make something the more people will be able to afford it and therefore want to buy it. When you are talking about information transfer, this just does not apply. Believe it or not, in the information arena, your price tag tells people what you consider to be the value of the information you have to offer. Make sure that what you charge is commensurate with the importance of the information you are providing and/or with the credentials of who is presenting the information.
In terms of the latter, remember… you would not expect to pay $5 to hear management tips directly from the lips of General Colin Powell. If you saw that advertised, you'd think it was a scam. On the other hand, some people would pay $100's of dollars just to hear him speak even if the topic was about something they were only peripherally interested in, just to hear his perspective. So keep the credentials of who is making the presentation in mind when you set your price.