Metrics
What your engineers actually had to do
Vacuum Effort is what the work should cost in a clean system. What your engineers actually had to do is the same finished changes in today's setup: the baseline hours multiplied by how much more expensive the interdependent architecture made them.
A 20-hour change can become 60 or 80 hours because the setup includes other modules, other teams, meetings, and reviews. Convert those hours with the loaded hourly rate and you get the today price. The gap between that price and Vacuum Effort is sync tax.