Even more importantly, and I wish I made this the title: How do you determine if any particular offer is fair or even good, in the absence of a lot of offers?
This is inspired by the Teespring (YC 13) ad on the front page right now that states, "Good salary, good benefits and good equity."
https://news.ycombinator.com/item?id=5545443
Don't expect the real 'good benefits' where you get a company-paid flex benefits card and if you thought you might see a pension you should have a laugh and go outside & take a walk.
If it's an established company, you can/should use salary.com for ballparks on what is competitive.
If it's a startup, they are often preserving the small capital they have (cash poor), so you're looking at "Ramen" salaries (~$50k) or no salary at all, and bigger chunks of equity. (That equity will be worth zero or something based on your work & your small team's work, & luck.)
But, the best benefit is to make your living expenses while learning & saving a bit. The learning part is what most people forget about when picking a job.
The usage is essentially an employer trying to set an early anchor for bargaining that is blessed as "good" by both parties.