Costful XML sql operation

This query works, but it's cost is very big, how to get same result but with less cost?

SELECT ProductID, Split.a.value('.', 'NVARCHAR(60)') ProductNumber FROM (
    SELECT ProductID, Cast ('<M>' + Replace(ProductNumber, ',', '</M><M>') + '</M>' AS XML) AS Data FROM Table
) AS A CROSS APPLY Data.nodes ('/M') AS Split(a)