I imagine FIRE advocates insist you can get ahead with their principles almost regardless of your income. It's abundantly obvious to me, though, that the numbers work out way better when you're, say, earning $150k gross, $115k net, and living on $40k so you can save $75k per year; versus earning $50k gross, $40k net, and living on $20k so you can save $20k per year. That's why when younger people tell me they're reading about FIRE I ask them if they've also considered how to solve for "E" in the E-S-G model.