Usage patterns
バーゲンで〈物〉を買うto buy something at a bargain sale
I bought a coat at the bargain sale.
バーゲンに行くto go to a bargain sale
I went to the department store's bargain sale with a friend.
バーゲンが始まるfor a bargain sale to begin
The summer bargain sale starts today.
〈物〉がバーゲンになるfor something to go on bargain sale
Winter items went on bargain sale.