Yes - highly variable.
To give you an idea of one system, at my institution, all faculty are given a salary (based on myriad factors). Then, the individual must "make" that salary. If you can get all the money through grants, then you only need to do enough clinic to maintain your certification/license (ie: 1/2 day clinic per week). So, you need to have enough grants to pay for your overhead and all the "stuff" that goes into research - and after you account for those costs, then you can pay into your salary. This may take multiple grants (or some big RO1s) to make the needed dough.
If you are on the clinical track, then you need to make enough RVUs to make your salary. You cannot make more than your salary by getting more grants or seeing extra patients. The only way to get more money is through bonuses (seeing more patients can lead to productivity bonuses). The salary can increase, nominally, each year - but the only way to improve it substantially is by going up the promotion ladder. It also helps if you have offers from other institutions and your home institution counters to keep you.