RSUs are worth very slightly more than straight cash compensation due to the optionality. Your compensation will go up and down as the underlying stock moves, and you are allowed to switch jobs when the stock price moves downwards.
I'd rather have a dollar now versus the equivalence of a dollar in a stock which is unavailable for up to 4 years...
Even if your companies stock is out performing the market, I'd rather have a dollar now to buy company stock and keep my mobility.
Employees need to be careful to diversify their portfolio. A dollar today can be put in any type of investment, whereas RSUs can lead to folks having too much of their egg nest in one basket.
The 4th year of an RSU grant is just as unavailable as my base salary 4 years away.
Yes, there's the diversification problem but it's not like you have that same money upfront to invest in anything you want.
Suppose after some time you start looking for jobs again, get another offer worth $215k/yr, and the stock price has done some movement. If the price is above $115/share, this would be a pay cut, so you decline the offer and state what it would take to get you on board. If it's below $115/share, you accept the job offer and get a pay raise.
This is what I mean by "optionality" here. If your employer's stock does well, you get an automatic raise from staying put. If your employer's stock does poorly, you get a raise with effort from finding alternate employment. You are more exposed to upside than downside in your employer's stock - it's effectively a call option with a strike price equal to the difference between your current cash compensation and your best alternative to negotiated agreement.