Reprioritization often leads to partially finished work items. Those work items have just a small chance of being prioritized again. Even if they do get reprioritized, the product or the code base will be further along, which means the partially finished work item need to be redone or even rewritten from scratch.
All of this does not come for free. Sometimes there is lack of understanding from C-Level management as to what reprioritization actually costs. The intention of the burn money chart is to assign $$ amounts to partially finished work items to make the wasted resources visible to stakeholders.
Bottom line, having the amount of sunk costs in a chart, similar to a burn up chart, helps to get momentum at C-Level Mgmt, when it comes down to the initial question of the monetary benefit of transitioning to agile methods.
Reprioritization often leads to partially finished work items, which create rework. All of that does not come for free. Sometimes there is lack of understanding from C-Level management as to what reprioritization actually costs.
Use this guide to calculate the cost of reprioritizing WIP (work in progress) and bring it to light for stakeholders..
The overall goal of the burn money chart is to achieve momentum at C-Level management that changes are required because the organization does not act efficient. This could be changes at process level, like the way you interact or how to set up Sprints or more fundamental changes, like the actual framework you work in e.g., V-Model, Rolling Wave Planning, Scrum etc. depending on the amount of money burned due to reprioritization.