In the bargain is a colloquial expression which means "in addition to" or "as a bonus". There are several synonyms for this phrase that can be used interchangeably, depending on the context. For instance, the phrase "on top of that" can be used as a substitute for "in the bargain". Similarly, phrases such as "to boot", "additionally", and "moreover" can also be used in place of "in the bargain". These phrases are often used to emphasise an additional benefit or a bonus that comes along with a particular action or situation.