Based on rates I saw for Java developers while working at Accenture for a few years. I adjusted down, assuming individual contractors wouldn't be able to bill out at the same rate, I just didn't adjust down enough...
Accenture, I imagine, has a lot of overhead. Freelancers, in general, don't. I rent an office for $200 a month and buy a laptop maybe every other year. All my business comes in via referrals. So my costs are pretty negligible. Thus a lower rate.
