A price is only part of the decision.
Imagine a student choosing between a free economics workshop and a paid shift. The workshop has no admission charge, but attending still uses two hours. If working is the student’s next-best alternative, the value of that shift is the opportunity cost of attending.
Economists use opportunity cost to describe the value of the next-best alternative forgone. The idea applies to time, land, attention and public resources as well as money. A zero price removes one possible expense; it does not remove scarcity.
Choose the next-best alternative.
Suppose the student could work, revise for an exam or meet a friend. Opportunity cost does not add together all three alternatives. Only one could have occupied the same time. The relevant comparison is the best alternative the student would actually give up.
That value may include more than wages. The student might value revision or time with a friend more highly. Identifying the next-best alternative requires understanding the person’s circumstances and preferences.
The same question matters for institutions.
A library that already owns a meeting room may offer it to a learning group without charging rent. Yet using the room still has an opportunity cost if another valuable activity could have taken place there. If the room would otherwise have stood empty, the alternative use may have little value. Context matters.
This does not mean every free program should charge a fee. It means a useful evaluation asks what participants and institutions give up, alongside what they gain. Travel, timing and access to a device can all affect whether an opportunity is practical.
A better question to ask.
Instead of asking only “Is this free?”, ask “What would I otherwise do with these resources?” Then compare the expected benefits of the available choices. A worthwhile workshop can have an opportunity cost and still be the best choice.
Understanding a trade-off is a starting point for a decision. It does not determine the decision on its own.