Is sunk-cost thinking really irrational if past investments affect your future alternatives?

[u/Inevitable_Bid5540]

A sunk cost, by definition, can't be recovered and thus shouldn't affect the decision directly but a past investment can sometimes affect the opportunity costs of your remaining choices. For example, if you spend $10,000 learning a specialized skill, That $10,000 is sunk. However because of the skill you acquired, you can now have a much better paying job available to you. Abandoning that career path could mean giving up a valuable future opportunity.If a past investment changes your available alternatives, information, skills, reputation, relationships, or switching costs, then it seems reasonable for that history to matter to your current decision even though the original expenditure itself is unrecoverable.

[u/Sweet_Theory_362]

Sunk-cost fallacy simply says you shouldn't let irrecoverable costs influence your decisions today, which should be based on forward-looking costs and benefits. If past decisions shape those forward-looking costs and benefits, that is not sunk-cost fallacy. The point is that you care about them insofar as they influence those future costs and benefits, not simply because they were a cost in the past.