1. Irrational escalation

2. Escalation of commitment
The phenomenon where people justify increased investment in a decision, based on the cumulative prior investment, despite new evidence suggesting that the decision was probably wrong.

3. "In for a penny, in for a pound".

4. "Throwing good money after bad"

5. Escalation of commitment refers to a human behavior pattern in which an individual or group—when faced with increasingly negative outcomes from some decision, action, or investment—continues the same behavior rather than alter course. They maintain actions that are irrational, but align with previous decisions and actions.
Economists and behavioral scientists use a related term, sunk cost fallacy, to describe the justification of increased investment of money, time, lives, etc. in a decision, based on the cumulative prior investment ("sunk costs"); despite new evidence suggesting that the cost, beginning immediately, of continuing the decision outweighs the expected benefit. In the context of military conflicts, sunk costs in terms of money spent and lives lost are often used to justify continued involvement.
In sociology, irrational escalation of commitment or commitment bias describe similar behaviours; and the phenomenon and the sentiment underlying it are reflected in such proverbial images as "Throwing good money after bad" or "In for a penny, in for a pound".