There are local factors to take in to consideration. I managed a 100% remote team with team members in UK, Spain, India, China, Canada etc. The total cost to the company remains roughly same but the amount that goes to local taxes and what employee gets in hand varies by market. Europe has very high taxation, which does benefit the employee eventually. US has what it has but offers the employee very little in terms of benefit during their lifetime. Simply saying FB pays 1/3 of SF market doesn't make sense.