How in the world are you getting from $250k salary to $1M total cost? Stuff like office space and equipment/services, health insurance, HR overhead are constants per person, they don't scale up with salary. Are you assuming that some big bonus or grant package is necessary?
The trick with discussing any numbers like this are variables that none of us can know without more intimate knowledge of a firm. For example, my spouse works for an SV firm. His team is 100% WFH, 100% of the time. They have no permanently allocated office space in any of the company’s buildings anywhere in the world.
However, they’re paying out bonuses twice a year, annual (PB)RSUs, (specifically for us) around almost $30k/yr in employer contributions to health insurance and our HSA combined, music streaming subscription, and so on.
The benefits, the bonuses, the extras, they all add up and are all very company specific. I’m not saying you’re wrong by any stretch. But with the number of extra benefits, healthcare, and everything else that’s different from employer to employer, we are all just guessing.
Facebook employees make a lot more than 250k. Someone with Eric lippert’s level of experience probably makes well over 600-700k in total compensation - just see levels.fyi!