Table

Assume the key columns of table Costinformation are Mandant and Code, we can update its Pricetable by following steps:

1. Split each cell of the Pricetable to rows. This will use STRING_SPLIT, because it can only use CHAR(1)/NCHAR(1) to identify separator, I have to replace all CRLF( CHAR(13)CHAR(10) ) to CR( because CRLF is CHAR(2) ). I treat the Pricetable column as NVARCHAR, so I use NCHAR to declare separators, if your column is VARCHAR, please change NCHAR(n) to CHAR(n).
2. Adjust the price. STRING_SPLIT can assign an ordinal number to each value. In your case, the 1st row and 1st column of the Pricetable are headers, and the others are the price values. Your data uses German format digitals, so I have to convert them to numeric using PARSE(), and after calculating the new price, convert them to strings with FORMAT(), both of functions I have 'de-de' as culture parameter. Then UNION all header rows with price rows. NOTE: I'm assuming that all cells of Pricetable have values, otherwise you'll need to add some process steps before PARSE(). 
3. Aggregated price rows to one string. I'm using two GROUP BY SQL to do this. STRING_AGG help to concatenate strings in the correct order.
4. Update Costinformation with new Pricetable value.

I'm using CTE to make the process clear, you can find the condition which filter the rows that need to be adjusted at code line 11, and the percent value at line 18. This is not good to use, you'd better replace them with variants, or rewrite the process on other way.

Code is here

WITH SPLITED_ORG  --Split each cells of the Pricetable to rows, and filter the data which will be adjusted.
AS
(
	SELECT M.Mandant, M.Code, R.ordinal AS row_num, C.ordinal AS col_num, C.value FROM Costinformation M
	CROSS APPLY
		STRING_SPLIT( REPLACE(M.Pricetable, NCHAR(13)+ NCHAR(10), NCHAR(13)), NCHAR(13), 1) R
		CROSS APPLY
			STRING_SPLIT(R.value, NCHAR(9), 1) C
-- ******** CHANGE THE CONDITIONS BELOW TO FILTER THE DATA THAT WILL BE ADJUSTED 
	WHERE
		[Text] = 'Product Table 1'
)
, SPLITED_ADJ --Adjusting price
AS
(
	SELECT O.Mandant, O.Code, O.row_num, O.col_num, --Filter all rows contain prices value (row_num and col_num > 1)
-- ******** 1.05 = 105%, change this value to adjust price
		FORMAT(PARSE(O.value AS DECIMAL(8,2) USING 'de-de') * 1.05, 'N2', 'de-de' ) AS T
	FROM SPLITED_ORG O
	WHERE O.row_num>1 AND O.col_num>1
	UNION ALL
	SELECT O.Mandant, O.Code, O.row_num, O.col_num, O.value AS T  --Assemble back all header cells( row_num or col_num = 1)
	FROM SPLITED_ORG O
	WHERE O.row_num=1 OR O.col_num=1
)
, AGG_ROWS  --Assemble rows
AS
(
	SELECT Mandant, Code, STRING_AGG(T, NCHAR(9)) WITHIN GROUP(ORDER BY col_num ASC) AS row, row_num
	FROM SPLITED_ADJ
	GROUP BY Mandant, Code, row_num
)
, RESULTS  --Assemble to string
AS
(
	SELECT Mandant, Code, STRING_AGG(row, NCHAR(13)+ NCHAR(10)) WITHIN GROUP(ORDER BY row_num ASC) AS r
	FROM AGG_ROWS
	GROUP BY Mandant, Code
)
UPDATE C  --Update data with new Pricetable
	SET Pricetable = R.r
FROM 
	Costinformation C INNER JOIN RESULTS R
	ON C.Mandant = R.Mandant AND C.Code=R.Code