Opportunity Cost is a term used in economics to describe the relative yield of a choice between options made mutually exclusive by a limited resource. The primacy of resource management in starcraft lends to good examples. If I use a drone to scout then the opportunity cost of the drone is the mineral count that the drone could have gathered if used as a harvester. If the drone is used to harvest then the opportunity cost is the information that it would have gathered as a scout. Because time is a limited resource, any use of the drone carries some kind of opportunity cost. Starcraft is interesting because minerals and information are both very valuable so you have to make tough calls.
Opportunity cost exists in smash as well. In melee, the opportunity cost of any given action is the potential to perform a different action. This gets complicated rather quickly, but I think it’s an important concept to consider.
For Jigglypuff, the most common example involves her bair. Bair has a low-moderate reward and extremely low risk, even on whiff. If you use that math then committing to spaced bairs pays off over time. It is possible (common, even) to space bairs outside of a character’s range until they take a different position or get hit. This makes bair appear like a one step solution. In some matchups it effectively is. However, in others even though the risk attached to bair is low, the opportunity cost is quite high. It is active, but it is not proactive. Every bair is a commitment to the air and at least 31 frames of bair animation. Habitually using that time on a safe but low reward action will net you much worse results than a player capable of recognizing an equivalent or better option with a lower opportunity cost.
Example: If Captain Falcon dashes at puff she can jump away and bair. His options to directly punish a retreating bair are few and carry a high risk, so he’s likely to just take a bit of stage presence at most. However, by jumping away Puff is forfeiting her opportunity to react to Falcon’s potential action commitment (probably with crouch or with uptilt, options that on confirm can net a stock, not just 12%). It doesn’t matter if the Puff player reacts to Falcon’s movement if she is already committed to a lengthy animation.
Opportunity cost applies very frequently to Puff’s approaches. Remember, every bair is a 31f minimum commitment. Committing to bair now prevents you from committing to a slightly later bair, a moderately later bair, or sometimes no bair at all. Any one could situationally be the most effective. The opportunity cost of a preemptive attack is in this case both the potential to react to the opponent’s movement and the potential to keep your own intent ambiguous and difficult to react to. In this way even if a bair goes unpunished or even hits it can be a costly overcommitment in terms of what could have happened if you chose a different option or even a different timing.
When formulating strategy and making decisions, weigh the opportunity cost of an action beside its risk and reward as an additional axis.