Cheapest priced copy (Dragons of Tarkir): $0.49 at Card Kingdom, near mint, their price list as of .
Corpseweft 
Enchantment · Rare · Dragons of Tarkir · #92
{1}{B}, Exile one or more creature cards from your graveyard: Create a tapped X/X black Zombie Horror creature token, where X is twice the number of cards exiled this way.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dragons of Tarkir | 92 | Rare | $0.49 | $0.49 |
2 rulings from Wizards of the Coast
- 25 February 2015“Exiled this way” refers to that activation of the ability, not any creature cards that have been previously exiled.
- 25 February 2015Because exiling the creature cards from your graveyard is part of the activation cost, no player can respond to stop you from activating the ability by moving creature cards out of your graveyard.