DROP TABLE #C
CREATE TABLE #C
(
	ID		INT,
	ParentId	INT NULL,
	Name		VARCHAR(255),
	Cnt		INT
)

INSERT INTO #c(Id,ParentId,Name,Cnt)
SELECT 1, NULL, 'Готовый продукт',  1	UNION ALL
SELECT 2, 1, 'Сборочная единица_1', 2	UNION ALL
SELECT 3, 2, 'Сборочная единица_3', 1	UNION ALL
SELECT 4, 3, 'Деталь_1',20		UNION ALL
SELECT 5, 3, 'Деталь_2', 10		UNION ALL
SELECT 6, 2, 'Сборочная единица_4', 2	UNION ALL
SELECT 7, 6, 'Деталь_3', 5		UNION ALL
SELECT 8, 6, 'Деталь_4', 1		UNION ALL
SELECT 9, 1, 'Сборочная единица_2', 1	UNION ALL
SELECT 10, 9, 'Деталь_5', 5		

;WITH xxx AS
(
	SELECT 
		Id,
		ParentId,
		Name,
		Cnt,
		[Level] = 0,
		[FullCnt] = Cnt
	FROM #c
	WHERE 
		ParentId IS NULL
	UNION ALL
	SELECT 
		a.Id,
		a.ParentId,
		a.Name,
		a.Cnt,
		[Level] = [Level] + 1,
		[FullCnt] = a.Cnt * b.[FullCnt]
	FROM 
		#c	a
	INNER JOIN
		xxx	b
	ON
		a.ParentId = b.Id	
	
)
SELECT 
	Name,
	Cnt
FROM xxx
ORDER BY Id