Answer:
The non-monetary costs you might experience are the calories, time, and the energy that you will burn by doing additional 20 pushups.
Step-by-step explanation:
As for the benefits, you will lose some calories and gain better physique, strengthening your core. The benefits will certainly outweigh the costs, unless the person drops dead while doing the second act, but your gym teacher should know better. Another point is that not all costs and benefits can be quantified in monetary terms, or "measured in dollars and cents," which the above example has adequately illustrated.