1. I am working on this, but are you able to attach original excel?
2. What label do you want to show?
Excel sheet attached. Would like to show the 'Short Campaign Name' and 'Total Cost per Bar' on each bar.
I came to the conclusion that without changing your excel file, it is not realistic to do it in Tableau.
Any of existing info does not define the block of bar, then I cannot proceed further step.
First of all, your chart is not standard gantt which is made with continuous date, so I made it standard gantt.
I attached modified excel and actually the formula on excel which I believe can define the block of bar is a real key in this case.
If you already have this key, please use it.