Generally, I splurge on things that make me happy or healthy. Both have economics that pay off in the long term, which we humans are particularly ill-equipped to take into account properly. So I don't care how much I have to pay to swim, I don't care how much my meditation app is, it'll pay itself back if I merely keep at it (and if it's not stupidly expensive). I mean, I just posted my tech setup over in pubski and we can discuss the specs of each of those items at length but fundamentally, it makes happy every time I look at it. I grew up in a reformed protestant community in a lower class neighborhood with parents that scraped by. In other words, peak Calvinism. Spending was a sin, modesty and frugality a virtue and one shan't have more than one needest to survive. Which I don't entirely disagree with - I still can't help but feel bad if I buy the slightly more expensive peanut butter. But I am frugal only to the extent that it doesn't interfere with my happiness or health.
This is the one salient point I got from the documentary Minimalism before dismissing it as a long and very pretentious ad for a book tour: minimalism means being able to justify everything that you own, to you. Not to anyone else. If it makes sense, for you, to have something as part of your life, more power to you.