Which of the following scenarios illustrates consumer surplus?

Consumer surplus occurs when a consumer is willing to pay more for a good or service than the actual price they end up paying. In this scenario, the consumer demonstrates a willingness to pay $50 for a concert ticket but purchases it for only $30. This difference of $20 represents the consumer surplus, as the consumer benefits from paying less than what they were prepared to spend.

The other options do not reflect consumer surplus. In the scenario where a consumer pays the exact price they anticipated for a shirt, there is no advantage gained beyond the expected payment, resulting in zero consumer surplus. Similarly, while finding an item priced lower than its typical cost suggests some form of value, it does not confirm a surplus unless the consumer had a higher willingness to pay. Lastly, when a consumer refuses to buy a product due to its high price, they do not realize any consumer surplus because no transaction occurs. Thus, the only scenario that clearly illustrates consumer surplus is the first one, where the consumer pays significantly less than their maximum willingness to pay.