Cheapest priced copy (Mirrodin): $2.99 at Card Kingdom, near mint, their price list as of .
Timesifter 
Artifact · Rare · Mirrodin · #262
At the beginning of each upkeep, each player exiles the top card of their library. The player who exiled the card with the greatest mana value takes an extra turn after this one. If two or more players' cards are tied for greatest, the tied players repeat this process until the tie is broken.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $2.99 to $22.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Mirrodin | 262 | Rare | $2.99 | $22.99 |
8 rulings from Wizards of the Coast
- 1 December 2004Remember which player would have taken the next turn if Timesifter's ability hadn't triggered the first time. After Timesifter leaves the battlefield and all extra turns have been taken, that player takes the next turn.
- 1 December 2004If two or more Timesifters are on the battlefield, keep a careful record of which players get which extra turns. With two Timesifters on the battlefield, two extra turns are created for each turn taken.
- 1 December 2004A land card has a mana value of 0.
- 1 December 2004Each player must exile the top card of their library at the start of each upkeep step.
- 1 December 2004If multiple extra turns are created in a game, the most recently created extra turn is taken first.
- 1 December 2004Each time there's a tie for the highest cost, only the players involved in the tie continue.
- 1 December 2004If a player fails to exile a card, they can't take the extra turn.
- 1 May 2006In Two-Headed Giant, triggers only once per upkeep, not once for each player.