Hmm... I knew Zulrah was 2m+/hr at times if you're maxed but I had no clue questing was that profitable. My personal experiences of questing would have placed it as much lower than that. As for fire capes, I had no clue of the rate.
To add some figures, selling BA (playing on their account) is around 1-3m/hr but inconsistent, assuming you're good at BA. Selling BA leeches is a consistent 1.5m/hr.
Firecaping, skilling, questing are all really good if you just want a pretty decent starting income. If you get a big customer base it can get pretty good.