Fixed costs are sunk costs. What is sunk cannot be retrieved in the same condition. Fixed costs cannot be reversed, without loss. Machinery PURCHASED, already, cannot be SOLD, without loss, in terms of money. Fixed costs that are incurred are not RELEVANT for our decision-making. Costs that will be incurred, in any event, should not be considered in the decision-making. In other WORDS, the existing fixed costs, which cannot be saved, do not influence the decision as those costs are already incurred and cannot be reversed, whether the FIRMS makes or buys.

Fixed costs are sunk costs. What is sunk cannot be retrieved in the same condition. Fixed costs cannot be reversed, without loss. Machinery purchased, already, cannot be sold, without loss, in terms of money. Fixed costs that are incurred are not relevant for our decision-making. Costs that will be incurred, in any event, should not be considered in the decision-making. In other words, the existing fixed costs, which cannot be saved, do not influence the decision as those costs are already incurred and cannot be reversed, whether the firms makes or buys.