Cheapest priced copy (Fallout): $0.49 at Card Kingdom, near mint, their price list as of .
Fraying Sanity 
Enchantment — Aura Curse · Rare · Fallout · #459
Enchant player
At the beginning of each end step, enchanted player mills X cards, where X is the number of cards put into their graveyard from anywhere this turn.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
7 printings · $0.49 to $2.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Hour of Devastation | 35 | Rare | $0.99 | $1.99 |
| Hour of Devastation Promos | 35s | Rare | — | $2.79Out of stock |
| Fallout | 175 | Rare | $0.49 | $0.79 |
| Fallout | 459 | Rare | $0.69 | $1.49 |
| Fallout | 703 | Rare | — | $0.99 |
| Fallout | 987 | Rare | — | $1.49 |
| Wilds of Eldraine: Enchanting Tales | 19 | Rare | $0.69 | $1.49 |
2 rulings from Wizards of the Coast
- 14 July 2017Fraying Sanity's triggered ability counts the number of cards that were put into the enchanted player's graveyard during the turn, even if Fraying Sanity wasn't on the battlefield at the time those cards were put there, and even if those cards have left that graveyard.
- 14 July 2017The value of X is determined only as Fraying Sanity's triggered ability resolves. For example, if three Fraying Sanity Auras are attached to one player who had four cards put into their graveyard this turn, X will be four for the first ability to resolve, eight for the second, and sixteen for the third.