The phrase "for a song" typically means something that is sold or bought for an incredibly low price or at an incredible bargain. There are several synonyms that can be used to convey the same meaning, such as "dirt cheap," "a steal," "a giveaway," "a pittance," "a fraction of the price," "inexpensive," "affordable," "budget-friendly," "economical," "cost-effective," "marked down," and "on sale." These words can be used interchangeably depending on the context and the tone of the sentence, and they all help signify something that is extraordinarily cheap or at an unbeatable price.