Give all your alts at least skinning, and then either herbalism, or mining. Those are the actual money making professions. On my main I'm currently clearing 55g per stack of cobalt bars, and I can mine a stack in one evening of questing. I'm not sure what stacks of leather are bringing, but before I dropped skinning, for tailoring it made me enough to buy all the cloth I needed in the AH to take tailoring from 1-275 in one day.

I also know that at level 60 it's possible to take any of the gathering professions from one to 300 in about nine hours of play time. Might be possible to do it even faster now with the right class at 80.