TANSTAAFL is an acronym for the adage "There Ain't No Such Thing As A Free Lunch." The term was created by author Robert A. Heinlein in his book, The Moon Is a Harsh Mistress. The term refers to the fact that when a person, or group, delivers something apparently "for free," there are explicit or implicit costs incurred. The term is popular with libertarians.
An example of TANSTAAFL would be when liberals decide to use welfare to help the poor, ignoring the fact that it costs money to help the poor, and that there is an unintended consequence of creating an entrenched class of impoverished citizens with no incentive to improve their plight.
Implying that something is "free" does not mean there is no attached cost.