A social psychology term, referring to the practice of adding a higher cost to a contract after a person has already agreed to it, or of understating the true cost involved in an act. An example would be the charges for undercoating a used car salesman might attempt to add to the agreed-upon price. The person has already agreed to buy the car, so they are likely to pay small additional charges rather than walking away. Another example would be a military recruiter mentioning college grant opportunities while understating the possibility of being separated from your family and sent off to die in a war.

The low ball technique It is one of the three Compliance Traps, along with Door-in-face technique and Foot-in-door technique.

Influence: The Psychology of Persuasion by Robert B. Cialdini