Question about billable rate and salary

I have a question about billable hours and corresponding salaries. My work is mostly flat fee, so I'm not in a world where we have to deal with that and thought this community would be the best place to answer. If you're required to put in a certain number of billable hours per year/month/week, and your time is being billed to the client at a specific rate, is there any magic number or ratio of payments-to-salary? Like if I know I'm going to be making the firm $500k a year in my billable hours, should that equate to some level of compensation? Company says "you're going to make us $600k in billable hours, so your salary is going to be $200k."?