I've read a few articles about what the Berlantiverse actors were pulling down in appearance and autographing fees over the years; this one, from 2016, pegs Stephen Amell at a quarter of million for a weekend's appearance. Cynically, actors may look for a genre television gig to score conventions paydays like this.
On the other hand actors like Amell are on CW shows which probably don't pay as much the bigger networks and the money they make on the convention circuit in some ways would make up for it.