@Rachel Yaghoubzadeh
Per @Jaitabh Jewel Sharma's comment, it would be good to see a screenshot of what you are looking for. In the meantime, I took a look at your ask and tried to mock something up. Let me know your thoughts.

The above screenshot shows Application A and Application B, where they are both assigned to multiple Business Units. Cost column is the cost associated to the given Business Unit per Application. Total column is a sum of cost for each Application.
Data that was uploaded in the original table: Application, Business Unit, Cost
Total was calculated within the backing table using the formula:
=SumIf(Application,Application,Cost)
BU Cost % is = Table.Cost/TableTotal
**Table to be replaced with the name of your table where the data is being pulled from
Per your comments, you are filtering based on BU with the end goal that you will still see the % based on the total cost for that Application across all Business Units.

I've filtered on a specific Business Unit. You will see that the BU Cost % is still based on the overall cost of the Application across all Business Units in which it's being allocated to.
I've included all the columns for a visual example, but you can chose to show/hide as you see fit.
Let me know if that helps!
Rob Anderson