And my point is that I, as a combat pilot, earned more per hour than all those methods. I didn't play all day every day for a week. I think the most I did on any given day was 4 hours, the other days were 0-3 hours - even counting the parts of those hours where I was crashing to a black screen, summoning Task Manager, being frozen mid-fight for 30 seconds at a time, etc. etc. So it works out to something like 2 billion a day if I'd dedicated my life to it, based on the 8 hour working day that you need to get a billion in opals.
I mean, I think it's ludicrous, actually. The method we used is no secret: whether you think it's an exploit or not is a subjective decision, but the basics have been in the game for a couple of years and it was clearly a conscious design decision. But 3.3 buffed the payouts to silly levels. And I certainly wouldn't call it "high risk".
The better question is, why do it, when there's absolutely nothing to spend your billions on?