SQL Server 2019

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CREATE TABLE dbo.tablename
(Price_one int, Price_two int, Price_three int, Price_four int);

INSERT dbo.tablename(Price_one, Price_two, Price_three, Price_four)
VALUES
(204,	204,	204,	204),
(208,	208,	208,	208),
(212,	212,	212,	212),
(206,	195,	187,	204);
4 rows affected

UPDATE dbo.tablename
  SET Price_two   = NULL, 
      Price_three = NULL, 
      Price_four  = NULL
    WHERE Price_one   = Price_two
      AND Price_two   = Price_three
      AND Price_three = Price_four;
3 rows affected

SELECT * FROM dbo.tablename;


Price_one
Price_two
Price_three
Price_four


204
null
null
null

208
null
null
null

212
null
null
null

206
195
187
204

Price_one	Price_two	Price_three	Price_four
204	null	null	null
208	null	null	null
212	null	null	null
206	195	187	204