Besides the five-year plan, the most easily accessible public records would be the Annual Report and the monthly reports from the Infrastructure V.P. and the Treasurer.
I don't know that there's a more granular breakdown of Infra's budget available online. For what it's worth, the biggest single expense, for many years, has been sysadmin labor. Bandwidth also looms large, though last I knew much of what the ASF used was provided by OSU OSL and SourceForge.
https://www.apache.org/board/plan.html
https://s.apache.org/FY2018AnnualReport
https://whimsy.apache.org/board/minutes/Treasurer.html
https://whimsy.apache.org/board/minutes/Infrastructure.html
I don't know that there's a more granular breakdown of Infra's budget available online. For what it's worth, the biggest single expense, for many years, has been sysadmin labor. Bandwidth also looms large, though last I knew much of what the ASF used was provided by OSU OSL and SourceForge.