SQL Query Result without ISNULL

Hello Community,

The following query will convert NULLs to zeros:

SELECT MakeName, ModelName ,Cost + RepairsCost + ISNULL(PartsCost, 0) + TransportInCost AS TotalCost
FROM Data.SalesByCountry

Can someone let me know how achieve the same result with ISNULL?

The tables and data is a follows:

CREATE TABLE Data.SalesByCountry (
CountryName NVARCHAR(150) NULL
,MakeName NVARCHAR(100) NULL
,ModelName NVARCHAR(150) NULL
,Cost MONEY NULL
,RepairsCost MONEY NULL
,PartsCost MONEY NULL
,TransportInCost MONEY NULL
,Color NVARCHAR(50) NULL
,SalePrice NUMERIC(18, 2) NULL
,LineItemDiscount NUMERIC(18, 2) NULL
,InvoiceNumber CHAR(8) NULL
,SaleDate DATETIME NULL
,CustomerName NVARCHAR(150) NULL
,SalesDetailsID INT NOT NULL
)
GO

Data

Why would you want that?