Cheapest priced copy (Pro Tour Collector Set): $6.49 at Card Kingdom, near mint, their price list as of .
Howling Mine 
Artifact · Rare · Ninth Edition · #298
At the beginning of each player's draw step, if this artifact is untapped, that player draws an additional card.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
34 printings · $6.49 to $1799.99 at Card Kingdom
4 rulings from Wizards of the Coast
- 4 October 2004If Howling Mine leaves the battlefield before it resolves, then the last known tap or untap state of the card is used for resolution.
- 4 October 2004The additional draw is separate from any other draw during your draw step. It happens when the triggered ability resolves.
- 4 October 2004It does not trigger at all if this is tapped at the start of the draw step, and it checks this again on resolution.
- 15 April 2013The triggered ability is put onto the stack after you have already drawn your card for the turn.