Glassdoor doesn't look at the tax differences (use a tax calculator), the fact that Google gives you 8.5% pension that you can use either to buy a flat (I have done it from my Swiss pension money), create a company or use it in emergency, and also you can take it out (after paying taxes) if you leave the country. Also I don't believe the 200k pound figure for Facebook London as a median compensation package. Can somebody confirm it?