Lying for one dollar makes the lie more convincing. To yourself.
In 1959 Festinger and Carlsmith had students do a mind-numbing task, then tell the next participant it was exciting, for 1 or 20 dollars. The 1-dollar group afterwards rated the task as more interesting. 20 dollars justified the lie; 1 dollar didn't, so the brain adjusted the opinion. A clash between doing and thinking is uncomfortable; the thinking usually yields.
Useful: Whoever gets you to take a small action often shifts your attitude along with it.
Source: doi.org