In Washington DC (and many other cities, I'm sure) public transportation has tiered pricing, which means that fares during rush hour are higher than non-rush hour fares. Usually this doesn't make much difference to me; I pay whatever the fare costs when I need to ride.
But every so often, I find myself standing at the entrance to the station just before 7pm (when the prices switch over), thinking: "Do I catch this train, or wait 5-7 minutes for the next one and save 80 cents?"
Of course, $0.80 is not much money at all to be concerned about. But on the other hand, how much difference does a few minutes make? I usually have a book to read or something else with me to occupy my time.
In the end, I usually make different decisions on different days, depending on how tired I am and if there's a particular reason to get home quickly. I'm more likely to just get on the train and pay a little more, but there are certainly times that I've waited the few extra minutes.
Do you pay attention to little trade-offs like these, or do you figure they're not worth worrying about?