Dis-incentive them with a visible cost or better yet by total man hours.

https://bloomberg.com/news/...

I did that once at the end of a meeting.
I had a slide with the minimum and maximum cost of the meeting like this: average people gross salaries x hours < $ < billable $ to customers x hours

It was a meeting in which the department Head said we were not going well and he couldn't afford to hire more people.

There were some funny faces around.
I wasn't very successful with that boss, though.