The average developer salary is approx. $20 per hour or $40,000 annualized. This includes benefits.

Dividing by $40,000 by 1200 gives you $33 per hour. Assuming that you work out of your home, you want to add a multiplier of 1.5 to get $60 per hour. Now throw in a 20% profit margin ($12), and you get a final rate of $72 per hour.