[karterk]

While I don't know the details of this offer, I would strongly advise you to give it a pass. Such a paycut will rarely compensate you fairly even if your start-up ends up being a moderate success (~200 M exit). Unless this company already has a terrific traction and you get a significant chunk of the options, there is no point in a 50% pay cut.

There are also several gotchas around start-up options. You should read this: http://blog.samaltman.com/employee-equity