to include sth with what you are selling or offering, without increasing the price
throw sth in
to include sth with what you are selling or offering, without increasing the price
You can have the piano for $200, and I'll throw in the stool as well.
throw sth in
to add a remark to a conversation
Jack threw in the odd encouraging comment.
Definiciones del Oxford Advanced Learner's Dictionary, 9.ª edición