Cheapest priced copy (Mirrodin): $1.49 at Card Kingdom, near mint, their price list as of .
Spellweaver Helix 
Artifact · Rare · Mirrodin · #247
Imprint — When this artifact enters, you may exile two target sorcery cards from a single graveyard.
Whenever a player casts a card, if it has the same name as one of the cards exiled with this artifact, you may copy the other. If you do, you may cast the copy without paying its mana cost.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $1.49 to $14.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Mirrodin | 247 | Rare | $1.49 | $14.99 |
12 rulings from Wizards of the Coast
- 4 October 2004If this card leaves the battlefield while the ability to make a copy is on the stack, the ability will still make a copy using the last-known-information rule.
- 4 October 2004If the imprinted card leaves the exile zone while the ability to make a copy is on the stack, then no copy will be made.
- 1 December 2004You cast the copy while this ability is resolving, and still on the stack. Normally, you’re not allowed to cast spells or activate abilities at this time. Spellweaver Helix’s ability breaks this rule. (The card that triggered this ability is also still on the stack.)
- 1 December 2004If the two imprinted sorcery cards have the same name and a card with that name is cast, only one copy is created, not two.
- 1 December 2004If you don’t want to cast the copy, you can choose not to; the copy ceases to exist the next time state-based actions are checked.
- 1 December 2004If there’s only one imprinted sorcery card, nothing happens.
- 1 December 2004You don’t pay the spell’s mana cost. If a spell has X in its mana cost, X is 0. You do pay any additional costs for that spell. You can’t use any alternative costs.
- 1 December 2004You can’t cast the copy if an effect prevents you from casting sorceries or from casting that particular sorcery.
- 1 December 2004You can’t cast the copy unless all of its targets can be chosen.
- 1 December 2004Spellweaver Helix’s second ability creates a copy of the imprinted card in the Exile zone (that’s where the imprinted sorcery card is), then allows you to cast it without paying its mana cost.
- 1 March 2005The creation of the copy and then the casting of the copy are both optional.
- 18 April 2017A split card has the same name as a spell if either of its names is that spell’s name.