The Sunk Cost Fallacy describes our tendency to follow through on an endeavor if we have already invested time, effort, or money into it, whether or not the current costs outweigh the benefits.

This is why a lot of people stay in bad relationships because they have already spent time in it and they think will lose if they break up. Companies use this technique to make investors invest more money into failing projects since they have already spent money in it and might as well spend more to make sure it doesn’t go wrong.

You can use this as a tactic to get your existing customers to buy more products as “upsells” after they have invested the initial amount to get started because the customer will feel as if they might as well spend more money!