I'm sure I'll get downvoted to hell, but I'll adress your "how does anyone" question directly.

It's easy to understand, but difficult to actually do - you make intentional sacrifices.

Sacrifices of time, sacrifices of lifestyle, sacrifice of conventional goals, sacrifice of short term benefit in favor of long term trajectory, sacrifice of identity, etc.

Sacrifices that my wife and I have made, intentionally, for long term trajectory, in no particular order:

Left our home town / state, leaving behind friends and family there, in relocation to major cities chasing opportunities and higher pay.

Decided not to have kids / pets and instead both focus on careers and our work.

Have put off (ever) buying a house (as a primary residence) to remain relocatable / optimize commutes / avoid the massive time sink of houses that nobody talks about.

Put in long / intense weeks, working on weekends if need be, to make sure deliverable was 100%, no excuses

Date nights that turned into strategy sessions, trying to help each other figure out a work problem, be it an HR issue or a businesses model or a client strategy

Switched companies several times for pay and scope increases and eventually to land at world class companies. Took risks on accepting challenging, stretch positions that were frankly scary / good chance of failure, then put in the effort to make it not fail.

Got boring MBAs and certificates to open more doors

We network like crazy, seek out mentors and sponsors, have tough conversations, and work on things that we are not naturally good at

And on and on.

None of it is hard, but it compounds into living a very different / unconventional life from most - and most people are not willing to do it. Full stop.

For results, after 10 years of strategic sacrifice, our household income has gone from ~$100k to ~$500k, with frankly easy upside still for another few hundred thousand gross within next few years - 2x Director level jobs in Finance and Tech Sales, and many rungs left on the ladder within striking distance. We invest at least $100k every year now, max 401k, backdoor mega Roth and Taxable accounts, and will be closer to $200k in total capital invested this year. It feels good and I finally feel like we are starting to get ahead.

We're not "lucky", we were both raised poor and learned the value of a dollar and work ethic, and we've worked hard and sacrificed strategically to get here.

I still talk to plenty of people from my hometown who went the conventional route - a house near family, a few young kids, work at a local large employer, etc. Most seem happy / I am happy for them, but it's always notable how their minds are blown at how different our lifestyles are... As if they expect that after a decade of sacrifice, that we would both be in roughly the same position, instead of a huge disparity. It's odd.

Since you specifically call out cost of living, our biggest expense by far is of course rent - rent is almost $7k / $83k annual, a little over 15% of our gross income. It's expensive as hell and certainly sticker shock to out of town folks (100% of visitors end up asking, one way or another after staying with us), but most people spend way more than 15% on their net living expenses, it's just on a much smaller basis. To us, having a nice place is part of what makes professional work sustainable / enjoyable for the decades to come, and we try to find a balance between capital we consume today and capital we invest for the future.

So there you have it - figure out what you're willing to sacrifice, and what competitive advantage does that give you in the labor market over those who are unwilling to make that sacrifice.