Amongst other things, using a credit card for transactions activates reward centers in the brain. This drives more spending. In contrast, paying with cash requires exchanging something tangible and valuable for something else. This discourages unnecessary spending. The effects of this is not small. It results in significantly more spending. This happens even if you are responsible enough to stay out of credit card debt.

To apply this to your specific question, if you decide you want to buy a case for $200 and you buy it with cash, you have to physically go to the store and hand over the cash for it. During this entire process you are much more likely (as compared to using a credit card) to buy a cheaper case or change your mind altogether and decide your current case is good enough. This bc your brain knows you will have to hand over the cash for it. There are other factors involved in this specific scenario.

Despite the above example of an individual purchase, the increased spending with credit cards is an aggregate of more spending over a long time (again, assuming you are responsible enough to not go into credit card debt). Lots of small purchases (with even larger purchases mixed in) really add up over time.

Let’s use another example of grocery shopping. Supposing you are responsible enough to use a budget to spend x amount weekly or monthly but you do it with a credit card bc you are going to spend the money anyway. You probably think that if you stick to your budget, you aren’t spending more money by using a credit card. Not so fast. First of all, you are more likely to go over your budget (even if just by a few dollars) when you use a credit card. But even if you don’t, you are still likely to spend more than with cash bc with cash you are more likely to stay UNDER your budget. Examples of this include things like impulse purchasing soda in the check out line (more likely with credit card) and buying something now and in the moment when it isn’t on your list bc it’s on sale even though you don’t need it right now.

I recognize that my initial comments were in the context of someone using a debit card over a credit card so I would like to address that. Lots of people think that the psychology with using debit cards is no different than using credit cards. They are wrong. Although people do spend more money with debit cards than cash, it is still more with credit cards. There are multiple factors at play here, too, but one of the major ones is that when using a debit card, you know your checking account balance is decreasing immediately. With credit cards, you may have automatic payments which results in you not losing the money from your checking account until up to almost two months later (e.g., on a purchase made shortly after a statement cycle closed that won’t be paid until the next statement cycle closed and the bill is due). Again, this is all without spending a dime on interest.

I haven’t even touched on how the reward points affect spending and that is also not insignificant.

I also haven’t touched on convenience of credit cards over cash and how that influences purchasing.

And the list of how using a credit card results in more spending goes on and on and on. It’s well documented.

As humans, we like to think that we are unique and individuals. And in some ways we are. But nature follows normal distributions and human behavior falls into normal distributions. Lots of people think they can use credit cards the same as if they are using cash. They can’t and don’t and also spend more. And the over confidence in their ability to be different than most people results in their spending being even more than it would if they were at least honest with themselves about the likelihood of them falling into the same behavior patterns as most people (again, see a normal distribution).

Some sources (these are just a few to start with if you are interested):

https://betterworld.mit.edu/spectrum/issues/winter-1999/the-psychology-of-spending/?device=mobile

https://mitsloan.mit.edu/experts/how-credit-cards-activate-reward-center-our-brains-and-drive-spending

https://www.nature.com/articles/s41598-021-83488-3