It's worth noting that this is targeted at FIRE folks - people who want financial independence (don't need to work to live) and want to retire early. To be able

It's worth noting that this is targeted at FIRE folks - people who want financial independence (don't need to work to live) and want to retire early. To be able to retire 10+ years before the average american, you want to have a much higher degree of confidence that your financial plan can sustain you for 30/40/50 years. That requires much more complicated financial planning. Or you can just max our your 401k, IRA, HSA, save enough of what's left over to make sure you can have a comfortable retirement at 60ish. The math for everybody else actually isn't as tricky as it seems for mid-to-high income folks. It's generally more about reigning in spending than fancy spreadsheets.