Everything I've heard from people I know who organize events is that cancelling is very, very expensive and gets more so the closer you are to the date. Venues carve that space out for you and expect your attendees to spend a certain amount on food and alcohol. When you cancel, they're out a lot of money. Both from your event and the event they could have booked. That's why it gets more expensive as it gets harder to find a replacement.

Yes, it’s expensive, but usually not more expensive than actually going there (including incidentals like Uber rides, bar tabs, etc).

The only thing is, you save ~30-60% of your money, but when compared to salaries, it’s probably not enough to make a meaningful difference. Anyway, it’s usually not just about the money, but getting away and doing stuff as a team (even if the team doesn’t know about the layoffs).