Gilbert Quevauvilliers performs some measurements:
Before using Fabric Capacity operation events, you need to have a Fabric capacity.
In my testing, Capacity Operation Events consumed approximately 230,000 CUs per day.
Based on my usage, an F4 capacity was required to run this continuously each day.
NOTE: This is based on my usage. Your consumption may be slightly higher or lower.
That’s a fair amount of capacity to track how much capacity you’re using.