Some of those hotel prices are due to brand names. And aren't a lot of Ted talks posted free online now?I understand. For you the lectures are a business proposition; a marketing opportunity. If you charge $50/hour you will get $50/hour customers; if you charge $120/hour you will get $120/hour customers. You just have to make sure that the experience and the price match. Perhaps you could test a more expensive lecture that provides a different and more robust experience. It would be a way to see if there are any $120/hour customers.
Why do people spend $350 a night at a Ritz Carlton when there is a $125 a night Holiday Inn down the street? The experience is better. It costs $5000+ to attend a Ted Talk.