In my brother’s company, they don’t pay anyone that much (yet), but what they’ve done to keep most of their juniors is to bump their compensation quite a bit when it’s clear that they have high potential
and are realizing it. So raises end up being on the order of $10k+ a year in some cases. Combined with increased benefits (time off, etc) the longer you stay with the company, and they’ve found a formula that keeps their employees from jumping.
If you think about it from the perspective of the employee, you are working for an employer who is giving you sizable raises, continual career growth, long term benefits, and a team you enjoy working with. You can perhaps maximize your pay by going through the whole interview cycle and ending up with $10-20k bump, but is that worth it? There is no certainty that the next employer gives such large raises or invests in employees.
As for your case - $80k to $300k jump - that is exceptional. It is not going to be the norm. Not if continual investment happens. Based on your example (10 yrs experience), if they kept investing in that employee, they would have surpassed $100k long ago. If they hit the salary ceiling after 4-5 years, then conversations would shift. Maybe more days working from home, etc.
In my opinion, if you see such jumps happening regularly, then it is 100% on the employer for creating an environment that breeds large wage-skill gaps.