Whenever I've needed a big chunk of cash, I make a legendary and sell it. That won't work for everyone but at least at the rate I go through money it sets me up for a long time and makes the effort worth it. Another option for slow and steady progress is flax farming. Park a bunch of alt characters at the circle in Mount Maelstrom with reaper's sickles and then sell vials of linseed oil. For the effort and time it's a good return.