tsunamifury said pay, not cash salary... There's more to pay than cash, especially for private companies.

Comparing two offers where one is cash + liquid equity (the case at most major tech companies) and the other is the same amount of cash + equity in a company that has no near-term plans to IPO (the case at Uber), most people would consider the first offer to be worth more.

Even if nominally the equity is worth the same in the both cases, liquidity is also valuable. (And the equity might not really be worth the same--companies have been forced to IPO at a valuation lower than their last round of funding.)

Stock is exactly the same as cash to me, since I always sell all of it on the day it vests. Why would you only compare cash salaries when evaluating compensation? That makes no sense.

Uber explicitly prohibits stock sale on the secondary market, and their options expiry after 30 days of leaving job (instead of the standard-but-undesireable-still 90 days).