それだと[products].[price]の後が何だか分からん。

[products].[price]を求めるSQLをそのまま書くかJOIN使った方が良い。

UPDATE [working]
SET [working].[value] = (SELECT [products].[price]
FROM [products]
WHERE ((([working].[name])=[products].[name])));

UPDATE [working]
INNER JOIN [products]
ON [working].[name]=[products].[name]
SET [working].[value] = [products].[price];

スマホからテキトーに書いてるので間違ってたらスマン。