Actually, those terms are deceiving. First, getting 2000 billable hours is not a practicable estimate. 1200-1500 is reasonable. Also, the overhead for an independent has a higher tax rate and foots the entire insurance (health and liability) bill. The list of overhead goes on, but those are the big boys.
Plumbers are a minimum of $80/hour. Are you saying you value yourself at less than half of a plumber?