DECLARE @Price TABLE (Id int, sprice varchar(100))
INSERT @Price VALUES (1, '100.0:5000.0'), (2, '200.45:750.1')

;WITH CTE AS
(
SELECT *
FROM @Price
OUTER APPLY
(
SELECT *, 
       ROW_NUMBER() OVER(ORDER BY 1 / 0) AS rn
  FROM STRING_SPLIT(sprice, ':')
) c
)
SELECT Id, TRY_CONVERT(DECIMAL(19,2), [1]) as Price1, TRY_CONVERT(DECIMAL(19,2), [2]) as Price2
FROM (SELECT Id, rn, value FROM cte) a
PIVOT (MAX(value) FOR rn in ([1],[2])) pvt


Id          Price1                                  Price2
----------- --------------------------------------- ---------------------------------------
1           100.00                                  5000.00
2           200.45                                  750.10

DECLARE @Price TABLE (Id int, sprice varchar(100))
INSERT @Price VALUES (1, '100.0:5000.0'), (2, '200.45:750.1'), (3, ':22.33')

SELECT Id, 
       TRY_CONVERT(DECIMAL(19,2), SUBSTRING(sprice, 1, CHARINDEX(':', sprice) - 1)) Price1,
       TRY_CONVERT(DECIMAL(19,2), SUBSTRING(sprice, CHARINDEX(':', sprice) + 1, LEN(sprice))) Price2
  FROM @Price

SELECT Id, 
       CONVERT(DECIMAL(19,2), SUBSTRING(sprice, 1, CHARINDEX(':', sprice) - 1)) Price1,
       CONVERT(DECIMAL(19,2), SUBSTRING(sprice, CHARINDEX(':', sprice) + 1, LEN(sprice))) Price2
  FROM @Price

или

SELECT Id, 
       SUBSTRING(sprice, 1, CHARINDEX(':', sprice) - 1) Price1,
       SUBSTRING(sprice, CHARINDEX(':', sprice) + 1, LEN(sprice)) Price2
  FROM @Price