In los angeles we paid our interns 3200 - 4000 a month. There is a ramp up and learning curve for any intern, candice brings up a good point. If you are paying close to 70k for an intern, like some in the bay area do then you're better off finding a more qualified freelancer. Only if your strategy is long term team building with the intern would that make sense in an early stage start up.
Some funded start ups here pay their interns in the 15 range and give them boring tasks, in this case the interns may not stay and definitely don't want a job there after graduation. It's purely a resume builder for them at that point.