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For reference:
Cheap overseas outsourcing = $20-30/hour
Junior/entry-level contract rate = $50-75/hour
Competent developer (i.e. able to work well without need for help or guidance) = $75-125
Highly skilled professional (flies in to help, recognized industry professional, directs projects architecture) = $150-300
Jr: $50-$80/hr
Sr: $90-$150/hr1. Specialize & productize your output, then offer fixed pricing. Customer gets a predictable result for a predictable cost, you produce something you can estimate to good accuracy while earning a higher effective rate.
2. Retarget your deliverables on business value instead of a technical spec sheet, then charge accordingly.
Note that both of these involve business development strategies, not improved technical skills.
I know a couple people in the contracting business, and they all say that having their own app(s) in the App Store was the most valuable aspect for marketing.