Shannon is driving in downtown Santa Fe$.$ She is not very familiar with the area and is running late for her appointment. She heads to a nearby paid parking lot and is told that it costs $$20$ to park. Shannon is irritated by the price. Although there are likely other paid parking lots that are less expensive, Shannon pays the price to park there. Different cost considerations impacted Shannon's decision, but clearly one stood out over all the others. Which cost exerted the most influence over Shannon's decision to park in the $$20$ parking lot?