In addition to the introduction of the iPhone 6 and the Apple Watch, Apple has showcased a new payment system that could revolutionize how people pay for things. With Apple Pay, you can leave your credit and debit cards at home. In terms of ease and convenience, Apple hopes its system will be an evolutionary leap from the era of cards.

The majority of the critics are focused on problems with virtual security and privacy. But another more important problem may need to be considered: When payment becomes easier, and when people don’t see the money they’re handing over, they tend to spend a lot more. As payment becomes more automatic, people become less sensitive to what they’re spending
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The reality is striking. People who use credit cards tend to spend more and are more likely to forget, or to underestimate, the amounts of their recent purchases. A recent study in Denmark, made public this year, finds that when university students use debit cards rather than cash, they are willing to spend significantly more on coffee and beer.

These new electronic payment options may affect retail pricing decisions as well. MIT’s Amy Finkelstein found in 2007 that when toll facilities use electronic collection, toll rates end up significantly higher. The increased use of electronic toll collection produces a 20 percent to 40 percent increase in rates, apparently because payment is less obvious to drivers.

To be sure, electronic tolls are even more automatic, and less visible, than what Apple has in mind. But it is a safe bet that there will be an “Apple Pay premium” for the use of the new system. And if payment-by-phone turns out to be as fun and convenient as Apple hopes, that premium might be even higher than the credit-card analogue.

Apple Pay will probably be a great boon to both consumers and retailers. The convenience will certainly be a strong selling point. But as always, buyer beware. When payments are simple and easy and consumers are not using cash, there is the strong possibility that they will spend a lot more than they otherwise would — and regretting it later.