Maybe buying an iPhone will give that person temporary happiness but when a person spends that amount of money on investment without buying an iPhone, but in the future he will get a good amount of profit from this investment and it will be seen that he can buy more iPhones from the profit of that investment. But our brains think very little like this, we prioritize what we get in the short term or what happiness we get for the short term as opposed to spending money.
If you can afford an iPhone without it affecting your bank account, buy it. Where the problem lies is, if you are using your last amount in the bank to buy it. If nothing of such, go ahead and buy your iPhone. So far, it gives you joy. People spend thousands of dollars for enjoyment in a day and it didn't stop those who want to invest in Bitcoin to have a change of mind.
I hate to assume that those who bought an iPhone made the mistake of buying an expensive phone when that's what they wanted; they bought it according to their want or based on the type of work they do.