Cheapest priced copy (Double Masters): $0.35 at Card Kingdom, near mint, their price list as of .
Thraben Inspector 
Creature — Human Soldier · 1/2 · Common · Double Masters · #35
When this creature enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
9 printings · $0.35 to $29.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Double Masters | 35 | Common | $0.35 | $0.49 |
| Commander Masters | 66 | Common | $0.35 | $0.49 |
| Innistrad Remastered | 45 | Common | $0.49 | $0.49 |
| Innistrad Remastered | 301 | Common | $2.29 | $2.49 |
| Jumpstart 2022 | 255 | Common | $0.39 | — |
| The List | SOI-44 | Common | $0.49Out of stock | — |
| Regional Championship Qualifiers 2022 | 3 | Rare | $1.79 | $5.99 |
| Shadows over Innistrad | 44 | Common | $0.49 | $1.49 |
| Time Spiral Remastered | 305 | Special | $1.29 | $29.99 |
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 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.
- 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.