My record for an useless meeting was when the Lead Architect called an all-hands R&D meeting (40-50 people) for the whole morning (0800->1200)

It was him reading tickets off Jira and editing them and randomly asking people about clarifications.

I was a consultant at the time, billing around 100€/hour and there were others along with their own people. That meeting was a) completely useless for 95% of the people there and b) cost about 15k€ easily.