The problem with being human is that we all like to believe that we’ll all be better in the future: We won’t be late for work this week; We’ll remember our uncle’s birthday next year; We’ll pay the cable bill on time next month. People like the feeling of being in control, particularly when it comes to their own daily lives.

Reality, however, is much different. The truth is that most people struggle with deadlines. We pay our bills late; We forget to move our parked car during restricted hours; We show up at the airport with more luggage than we had anticipated bringing. For Spirit Airlines customers, this last oversight can cost as much as $100 a pop.

That’s right–Spirit Airlines is now charging customers $100 if they show up with a carry-on bag that they haven’t paid for in advance. Even for organized flyers, the airline charges a $35 fee to book a carry-on bag in advance and $50 to do it at the airport counter. We can’t quite predict the future, but we’re fairly sure that quite a few customers will object to this new policy!

Spirit Airlines, of course, claims that its strategy benefits consumers because the financial consequences will compel them to be more prepared and vigilant when packing for a trip–but that sounds a little disingenuous to even the most forgiving person. It’s like credit card companies stating that interest rates are there as friendly reminders to consumers that paying the full amount every month is as nice as birthday cake.

Many companies profit from human fallibility, and most of the public accepts that as part of business as usual. From $1 library fines to $100 late charges on a rent bill, people can accept responsibility for their own lives and finances–and the same rule applies to carry-on baggage fees. But has Spirit Airlines gone too far?

After all, we all make mistakes. Determining the moment at which a policy goes from acceptable to predatory is largely a matter of public sentiment. Soon the public will decide if cheap tickets prices are worth the gamble against their own limitations.

Public service reminder: the house always wins.