The market rate for a person with your skillset (which is only likely to include a commission or profit-share if you're expected to take responsibility for getting clients to spend more, or they can't afford to promise market rate)

The fact the firm might bill a client a large multiple of that for your time is irrelevant: they take on the risks and responsibilities associated with winning the business and overheads and probably add value to your time with some combination of reputation, proprietary data/software/methodology, other team members, training and support etc.