I've been involved with running events so I appreciate that things like venues, staffing, speaker expenses, etc can build up to a considerable amount and that those costs have to be met somehow.
If it's a case of the event not being financially sustainable without additional non-ticket revenue then maybe charging for videos is what has to be done, but if the videos aren't bringing in a significant revenue stream while presumably significantly reducing the number of viewers I'd have to ask if that's a worthwhile trade-off ?
Obviously the answer for that is going to be different if you're optimising for profit or for community benefit, but that's why I'd rather have community events run sustainably by non-profits than on a purely commercial for-profit basis.
[I have no issues with videos being charged for / with-held at the speakers request though]