My gut feel was that you can't be right, but it looks like you are: cutting 8000 employees * $500k/year total cost to company (rough but useful ballpark figure) is "only" $4B.

Cross-checking against actual expenditure, Meta spent $118B total last year, with the second largest component of total spending being stock comp at $42B, of which vast slabs went to the top leadership that's presumably also not getting fired.