Currently reports do not contain details on when a promotion code was applied

https://developer.atlassian.com/platform/marketplace/knowledge-base/promotion-codes-in-marketplace-reporting/#overview

This information should be displayed in the report

suggestion copied from: https://ecosystem.atlassian.net/browse/AMKT-15900

The add-on costs X
Atlassian takes 25%

So if sold by an AEP, the math should be:
Sale Price = X
AEP fee = Y = (20% of X)
Atlassian fee = Z = (25% of (80% of X))
Net $ = (X-Y-Z)

Of course if the Sale Price has a promotion attached to it, then it gets reduced by such amount, so that should be factored in too