Cheapest priced copy (Innistrad: Double Feature): $0.35 at Card Kingdom, near mint, their price list as of .
Spiked Ripsaw 
Artifact — Equipment · Uncommon · Innistrad: Double Feature · #487
Equipped creature gets +3/+3.
Whenever equipped creature attacks, you may sacrifice a Forest. If you do, that creature gains trample until end of turn.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Innistrad: Double Feature | 487 | Uncommon | $0.35 | $0.49 |
| Innistrad: Crimson Vow | 220 | Uncommon | $0.35 | $0.49 |