Indeed, one of the most difficult behavioral biases to overcome when investing is the sunk cost trap. Here's what you need to know. First of all, you need to know the definition of a sunk cost.

Opportunity cost vs. sunk costs Another concept in cost accounting is sunk costs. "Sunk cost refers to the past costs that you have incurred," says Ahren A Tiller, Esq., Bankruptcy Law Specialist.