>Are there other major costs to company of a full time employee that are significant relative to the salary?
Yes. There's accounting/budgeting/HR jargon of "fully loaded"[1] as in "fully loaded salary" or "fully loaded cost" of an employee -- which is a higher amount that's calculated by the company. The extra costs in a fully loaded salary include health insurance, 401k match, vacation, etc.
Depending on the company benefits and overheard structure, the fully loaded cost could be ~1.2x to 2x the salary. E.g. it costs the company ~$375k behind-the-scenes to pay the $250k the employee "sees".
Therefore, your intuition that $250k salary == $250k billed-by-contractor is actually not an apples-to-apples comparison. The $250k-contractor costs less than a $250k employee. Other non-salary reasons for contractors include having a flexible size workforce -- especially for non-strategic projects. Instead of bad press headlines announcing, "layoffs of X employees", just cancel the contract.
another part in the "fully loaded employee" is the cost of supervision and organizational overhead. most contract labor is costed as if it was "material", neglecting these costs.
(you could argue this is just an accounting trick..)
Yes. There's accounting/budgeting/HR jargon of "fully loaded"[1] as in "fully loaded salary" or "fully loaded cost" of an employee -- which is a higher amount that's calculated by the company. The extra costs in a fully loaded salary include health insurance, 401k match, vacation, etc.
Depending on the company benefits and overheard structure, the fully loaded cost could be ~1.2x to 2x the salary. E.g. it costs the company ~$375k behind-the-scenes to pay the $250k the employee "sees".
Therefore, your intuition that $250k salary == $250k billed-by-contractor is actually not an apples-to-apples comparison. The $250k-contractor costs less than a $250k employee. Other non-salary reasons for contractors include having a flexible size workforce -- especially for non-strategic projects. Instead of bad press headlines announcing, "layoffs of X employees", just cancel the contract.
[1] https://www.google.com/search?q=%22fully+loaded%22+salary