See how many build minutes are being used by users, build definitions, team projects and more - https://marketplace.visualstudio.com/items?itemName=ms-devlabs.BuildandTestUsage
Next to the already aggregation of total time spend per build, it would be great to also have the total time spend on failed builds.
I can imagine that this would be a column like "Failed Minutes" everwhere existing "Minutes" are occurring and would take into account the "result" part of the build details to correctly identify failed time.