Juniors definitely don't make ~250k. Mid level, maybe. Senior, definitely.
Most of the time it's due to having some leverage (multiple FAANG+ offers).
the SWE ladder requires/expects for an L3 to get to L4 by makes no such requirement to ever get to L5.
Also career and personal skill wise, it's good to see how other companies work. Pay is in many ways determined by your negotiation skills, and that is empowered by creating better BATNAs via interview skill.