Priority

Here is a column expression that shows one way to do it.  Just replace Price with your actual table name.

Priority =
VAR vThisCode = 'Price'[Code]
VAR vThisPrice = 'Price'[Haulier price]
VAR vRank =
    RANKX (
        SUMMARIZE (
            FILTER ( 'Price', 'Price'[Code] = vThisCode ),
            'Price'[Haulier price]
        ),
        'Price'[Haulier price],
        vThisPrice,
        ASC
    )
RETURN
    IF ( 'Price'[Destination exclusivity] = 1, 1, vRank )

Pat