When I've worked in Cali (temp contract employee), it was about the same as anywhere. I just turned down contract CWI with a world famous staffing agency for the laughable sum of $35.00/hour. No per diem just turn in receipts for flight, rental car, meal and etc. for reimbursement. My experience is that EVERYTHING is more expensive there except for fresh fruits and veggies. Housing, taxes, car insurance (I pay $22.00/month for liability here) are out of my comfort range.
All the big companies are there and they make no concessions for localities when it comes to pay rates.
Disclaimer... I've not conducted business in LA since 2009 so things may have changed a bit. But at 35/hr to have to live there, I'd rather club a rabbit off my back deck at home and eat hoffenfeffer with potatoes here than try to find a safe neighborhood and deal with traffic.