Cheapest priced copy (Eternal Masters): $0.35 at Card Kingdom, near mint, their price list as of .
Skulking Ghost 
Creature — Spirit · 2/1 · Common · Mirage · #143
Flying
When this creature becomes the target of a spell or ability, sacrifice it.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
3 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Eternal Masters | 107 | Common | $0.35 | $0.49 |
| Mirage | 143 | Common | $0.35 | — |
| The List | EMA-107 | Common | $0.35 | — |
2 rulings from Wizards of the Coast
- 19 March 2021If the spell that targets Skulking Ghost has no other targets, it won't resolve (because it no longer has a legal target after Gossamer Phantasm has been sacrificed).
- 19 March 2021Skulking Ghost's triggered ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.