The difference between billing rate and salary should be understood well before acting out something like this. There are people in the office whose work supports your efforts, but are considered indirect costs. Your charge rate must cover their salaries. It also has to cover the cost of equipment, facilities, fringe for all workers, etc.
If you truly respected your colleagues, you wouldn't approach this as a transaction that can be understood unless you know the overhead rates of your company.
This. I hear people often who see the top line and think that's the bottom line. 'They charge X but it only costs Y to make', and don't realize how many other things there are in between.
It does indicate what the market will bear. My charge-out rate was a 4x what my gross salary was. It was sort of irritating.
I understand supporting needed people like admins/secretaries and the accountants, and to a lesser extent, salespersons* as I certainly don't want their jobs, and they make my work life far easier. I've done some minor accounting stuff as a project manager and was forced to do admin stuff (time cards, word processing etc) and I didn't delight in those tasks. I mostly objected to supporting upper management getting paid big for making my work life more difficult.
I've thought that a fair contractor charge rate was about 1/3 to 1/2 of my wage-earner chargeout rate. I haven't been temped to verify this, as I'm happily FIRED
*However, hanging out with salespeople is hard on the liver due to excessive drinking. Also I have a gift of telling the truth and not being believable, so I suck at sales.
Oh yeah, I forgot that even I was not billable some of the time, like when I was on the MMM forum at work :-). My actual on-site work at the customers was basically about 2 months a year, with the rest of the year preparation for those two months.
Edit to note that I was sometimes "overhead" myself.