5 boxing I do the Shadow Vault trio of dailies every day... takes < 10 minutes without epic fliers. I also go kill 10 of the flying guys on the island and turn their corpses into ghouls, this takes 5-10 minutes including travel time between shadow vault and the island/ledge.

So 5 * 13g * 5 = 325G not counting any drops you get in 20 minutes a day. I make sure I NEVER miss these so am easily earning over 2K a week for 20 minutes time a day...