Unless you are employee #1-5, the correct approach to valuing equity is to not consider it to be worth anything. For employees 1-5, divide the numbers the CEO gives you by at least 10 to account for risk, and then demand a competitive base pay.
First off, the people you're negotiating with see it as valuable, so it's a very bad negotiating move to say, "Keep your dumb equity and just give me cash." You'd be slightly better off just pointing to their family photo and saying, "Wow, your kids are ugly." Second, going through the work of valuing equity is necessary to see how the investors (that is, they people actually paying your salary) look at the company. Third, on the off chance you are successful, you're going to really wish you took the equity part of the negotiation seriously.
The down votes on calling spade a spade demonstrate it quite well