What is "low-ball"

The low-ball is a persuasion and selling technique in which an item or service is offered at a lower price than is actually intended to be charged, after which the price is raised to increase profits.

An explanation for the effect is provided by cognitive dissonance theory. If a person is already enjoying the prospect of an excellent deal and the future benefits of the item or idea, then backing out would create cognitive dissonance, which is prevented by playing down the negative effect of the "extra" costs.