It's already been up on Frostmourne BMAH and it was gold cap bid within 20 minutes of it showing up. I don't like the chances of it showing up again any time soon or beating people to it.
Pretty much, the time spent farming it each week could go towards farming the 999k that will be needed to win the bid when it shows up on bmah, and you will probably be able to buy it before it drops.
It takes a total of 5 minutes per kill as we only do yogg. So spending 10-15 minutes a week farming gold would take a looooong time to get gold cap :).
Your logic is quite horrible, following it I wouldn't have Ony drake or Ashes, because you know; why spend time killing bosses instead of afking in SS for 6 months while I wait for it to pop up on the BMAH.