CREATE VIEW deve ser a única instrução no lote

Assim como o erro diz, o CREATE VIEW A instrução precisa ser a única instrução no lote de consulta.

Você tem duas opções neste cenário, dependendo da funcionalidade que deseja alcançar:

Coloque o CREATE VIEW consulta no início

CREATE VIEW showing
as
select tradename, unitprice, GenericFlag
from Medicine;

with ExpAndCheapMedicine(MostMoney, MinMoney) as
(
    select max(unitprice), min(unitprice)
    from Medicine
)
,
findmostexpensive(nameOfExpensive) as
(
    select tradename
    from Medicine, ExpAndCheapMedicine
    where UnitPrice = MostMoney
)
,
findCheapest(nameOfCheapest) as
(
    select tradename
    from Medicine, ExpAndCheapMedicine
        where UnitPrice = MinMoney
    )

Use GO após o CTE e antes do CREATE VIEW consulta

-- Opção 2

with ExpAndCheapMedicine(MostMoney, MinMoney) as
(
    select max(unitprice), min(unitprice)
    from Medicine
)
,
findmostexpensive(nameOfExpensive) as
(
    select tradename
    from Medicine, ExpAndCheapMedicine
    where UnitPrice = MostMoney
)
,
findCheapest(nameOfCheapest) as
(
    select tradename
    from Medicine, ExpAndCheapMedicine
    where UnitPrice = MinMoney
)

GO    

CREATE VIEW showing
as
select tradename, unitprice, GenericFlag
from Medicine;