Well leg length discrepancy is medically necessary, you can live with 1-2 cm discrepancy with minimal problems but more than that it will cause hip problems and arthritis and be very tough
But cosmetic is unnecessary tho, you don't need to be average height or anything, it's up to you and you can certainly live a fine life without cosmetic LL
And the vast majority of people who get this done in the US are probably not "crazy people" in the way you've describing it, you don't have to worry. 90% of the US diaries I've read involve someone who is actually very successful in pretty much all aspects of their life but simply have a lingering neurosis, and want to get rid of that neurosis. You can't really afford 90k without being in the top 5% of successful haha. The average joe is living paycheck to paycheck and is in debt. So saving up 90k already weeds out plenty of those actual severly mentally ill people who are like "ahahahhaah my height is causing all my problems including my debt and no job and why that barista is looking at me weird or why I am always being stared at ahahahah if I get height surgery I will be a Chad and get all Dem women's and get a 100k job!!!1!1!!1!" And weeds out 99.999% of people in general
You can certainly be a "normal person" willing to be crippled for a few months for gaining height, in fact that's how everyone in the US did it before 2018, before weight bearing nails existed and people essentially in wheelchairs for 6 months. Many are completely normal people who did make a choice to become a disabled person for many months. They are still normal, just felt the gain/loss or reward/risk benefit was worth it, but choosing to be in pain and disabled temporarily is worth it if height is truly actually holding you back from living your life to the fullest (you have job, friends, hobbies, goals, family, but the only problem is self confidence or lack of rather, due to height insecurities)
If u want to do this, just note it will be tough, and not how Debiparshad describes it like a walk in the park. But it doesn't make you anymore "mentally ill" than the person who wants a nose job or butt lift, just because the recovery is way more rougher and longer.The only difference is recovery time, but that doesn't determine your intention- to gain heighr. In fact brazilian butt lift has a death rate way higher than CLL, but that's irrelevant