My number's based on cost of living. At $100k, in the area I live in, I have a good standard of middle class living but I still have to work hard to save, go on vacations, and make major purchases.

At $200k, I could maintain the same standard of living, easily pay off all of my student debt in about a year (without sacrificing anything), easily buy a house, buy a new car outright after saving excess money for 3-4 months, pay for my kid's college education outright, and save a ton of money for retirement. At $100k, I constantly have to pick and choose which of these things I work on.

If I made $200k, living in the same area, I might not be wealthy in the grand scheme of things, but I sure would feel like it. About 70% of the negative stress in my life comes from anxiety about being able to afford everything my family will want and/or need eventually.

Interestingly enough, I have already lived through the experience of having my salary double almost overnight. I used to live in a relatively low-cost area, but I was still getting paid about $25k below market. Then I moved to a higher-cost area, and took a more advanced position at a company that paid a little more than market rate. Went from below $50k to just under $100k. The impact on my life was significant. I went from feeling poor and helpless to finally being able to breathe. I used to be depressed and angry all the time because I could barely take care of my family and my household. Now I'm more or less happy.

18-year-old self would be comparing with entry level, rather than senior level, salaries. If you account for both that and inflation, the right question is "how would your 18yo self feel about $45k/y?"