If there is no other opportunity to use a resource alternatively .
For example specific computer software, machines, research, development, etc.
We talk about "sunk costs".
As we in traditional economics only care about opportunity costs, they doesn't matter for rational decisionmaking.
Sunk costs are historical costs, so we aren't able to influence them anymore.
Sunk costs are fix costs, but not all fix costs are sunk costs.
Absolute main criteria for the concept of opportunity costs is the scarcity of resources.
If there is no scarcity, there is no sacrifice, so, there are no opportunity costs.
For example specific computer software, machines, research, development, etc.
We talk about "sunk costs".
As we in traditional economics only care about opportunity costs, they doesn't matter for rational decisionmaking.
Sunk costs are historical costs, so we aren't able to influence them anymore.
Sunk costs are fix costs, but not all fix costs are sunk costs.
Absolute main criteria for the concept of opportunity costs is the scarcity of resources.
If there is no scarcity, there is no sacrifice, so, there are no opportunity costs.