Opportunity Cost and Product Possibilities Frontier

The Opportunity Cost is what one gives up in order to pursue a different path. It is the next best option. If you decide to hang out with friends, you cannot do homework in that same time. Some Pokemon examples;

1. You cannot breed for Bagon Eggs and Oddish Eggs at the same time.
2. You cannot train if you are participating in the Pokemon Contests.
3. You cannot train your Beldum and train your Poliwag at the same time.
4. You cannot use an Omastar's Water Pulse and Rollout in the same turn.

You may say "But you can train 2 Pokemon at once, Brock, using the Exp. Share!" Well, not at the same rate. This leads us to the Product Possibilites Frontier, or PPF. 

You have a limited amount of time, you can only do so much. The above PPF depicts how many eggs of 2 different species one can hatch within an hour, I tested this myself. In the time it took me to get 4 Bagon Eggs, I could have gotten 6 Oddish Eggs. Of course, I could have gotten a mix of of those two numbers, using the same time space. For each Bagon Egg you produce, you could have produced 1.5 Oddish Eggs.

Point A and Point B are on the line, showing that by using all your time efficiently, you can get this many eggs at most. Point C shows an amount of eggs to be made without using the time efficiently. Point D cannot be reached at this time, unless there becomes a way to hatch eggs faster somehow.

The same principle applies to training your Pokemon.