Cheapest priced copy (Double Masters): $0.35 at Card Kingdom, near mint, their price list as of .
Magnifying Glass 
Artifact · Common · Murders at Karlov Manor · #255
{T}: Add {C}.
{4}, {T}: Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
Legal inCommanderBrawlStandardPioneerModernLegacyVintagePauper
5 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Double Masters | 269 | Common | $0.35 | $0.49 |
| Commander 2018 | 208 | Uncommon | $0.35 | — |
| Jumpstart 2022 | 95 | Uncommon | $0.35 | — |
| Murders at Karlov Manor | 255 | Common | $0.35 | $0.49 |
| Shadows over Innistrad | 258 | Uncommon | $0.39 | $0.49 |
3 rulings from Wizards of the Coast
- 8 April 2016You can't sacrifice a Clue to pay multiple costs. For example, you can't sacrifice a Clue token to activate its own ability and also to activate Alquist Proft, Master Sleuth's ability.
- 8 April 2016If an effect refers to a Clue, it means any Clue artifact, not just a Clue artifact token. For example, you can sacrifice Wrench to pay for Alquist Proft, Master Sleuth's activated ability.
- 8 April 2016Clue is an artifact type. Even though it appears on some cards with other permanent types, it's never a creature type, a land type, or anything but an artifact type.