Saying “Thank you” is important. If nothing else it’s polite, but for events, it’s important to realize, you’re the least important piece of the pie.
No one is buying a ticket to hang out with you. They’re coming to see the speakers, possibly to meet sponsors (especially if they’re looking for work). If you factor in at all, it’s a distant third.
For every event I organize I hand write thank you cards. Every speaker gets one (barring hiccups in the process, etc) when they check into the hotel or when they arrive at the conference.
I think too many event organizers forget that it’s not about them, they form a cult of personality around them as if their presence is the key. Sure great organizers do great events, but the ‘great’ part is the event, not the organizer.
I’ve thought about using something to automate my thank you cards, but realized that’s not what I’m about. Sure some have words crossed out, because my hand moved faster than my brain, sure I sometimes write them upside down, or misspell a word, but that’s what authenticity looks like.