Perhaps, but it's possible to invest in Google via the stock market. I'm not sure it makes sense to bake in the stock market performance of a public company when considering value of their "equity." It seems like you should be using whatever your standard discount rate (S&P 500 or NASDAQ)?
FANG equity packages are an implicit buy option that lasts 4 years. $1 million dollars of options that lasts 4 years is very expensive and very lucrative.
Plus in startup land, your missing that equity half, so you can't take that money and go invest it in google like you could working at FANG.
