Now let's look at E2 which will be the expectation value of a payout from investing your salary difference between a high paying corporate job and a startup. Let's set this number at a safe value of $50,000/year. Invest $50k a year for 10 years in some safe stock and bond mutual funds and I bet E2 and much higher than E1. Heck, invest $50k year in lottery tickets and you might make out better than working at a startup.
That's not to say you should ignore startup jobs. They have a ton of other benefits. Just seems like equity is not one of them unless you are a founder.
You can think of employee equity as insurance against "I joined Facebook early and all I got was this lousy t-shirt."
FWIW, I joined a startup as that third partner (domain expert + execution guy), taking 10% of the equity while collecting 70k/yr (my base rate is north of 200k/yr otherwise). It would have brutalized the startup's seed money and jeopardized them if I somehow didn't perform and deliver.
Edit: your point is that good engineers cost $150k (really closer to $200k with taxes, etc). That's correct. So what happens when these engineers as a group realize that taking $70k + 0.5% equity is not the same as taking $150k + full benefits elsewhere? What other options do startups actually have at that point? More importantly, will this point happen and will it happen soon?
Everyone keeps suggesting that when evaluating a compensation package, one should not count equity for anything since it's worthless. Well, it is nearly worthless, unless you happen to hit the startup that becomes Facebook, Google, Dropbox, etc. and you get in early enough (usually only employee #1 gets over 1%). So why bother even offering a worthless piece of compensation. The startup might as well include a bunch of lottery tickets with every paycheck instead.
So, there are several bad things that can happen with options/equity.
1. The company fails, the options are worthless
2. The company is moderately successful, but not spectacularly successful. If your unvested options are worth (say) $30k/year, then they have no reason to give you a $30k raise if market rates increased by $30k (either due to a better job market, or your increased experience).
3. The company is spectacularly successful, your unvested options are worth big $$$. Now, your employer has an incentive to cheat you. They can look for an excuse to fire you (not too hard with at-will employment). They can raise another round of financing with a liquidation preference, reducing the value of your common shares. They can block you from selling your shares (Uber did this recently). The executives can give themselves big options grants, further diluting your common shares (happened to Eduardo Saverin at Facebook).