Gastly

Gastly (055/91), the Common from Paldean Fates, has an estimated ungraded market price of about $0.15. Note: 29 other cards named Gastly exist across the sets Riffle tracks, at very different values; check the collector number.

This page covers Gastly (055/91), the Common (about under $1) from Paldean Fates.

The other versions: #177/162 from Temporal Forces (Illustration rare, about $80–$110); #57/144 from Skyridge (Common, about $29–$38); #109/165 from Expedition Base Set (Common, about $6–$8); #63/102 from Triumphant (Common, about $4–$6); #62/100 from Stormfront (Common, about $3–$5); #65/105 from Neo Destiny (Common, about $2–$3); #82/130 from Diamond & Pearl (Common, about $2–$3); #63/112 from FireRed & LeafGreen (Common, about about $2); #36/99 from Arceus (Uncommon, about $1–$2); #33/62 from Fossil (Uncommon, about $1–$2); #76/110 from Legendary Collection (Common, about $1–$2); #52/92 from Legend Maker (Common, about $0.90–$1); #50/102 from Base Set (Common, about $0.80–$1); #75/130 from Base Set 2 (Common, about $0.70–$1); #64/99 from Arceus (Common, about under $1); #33/83 from Generations (Common, about under $1); #67/214 from Unbroken Bonds (Common, about under $1); #68/214 from Unbroken Bonds (Common, about under $1); #47/108 from Evolutions (Common, about under $1); #36/111 from Crimson Invasion (Common, about under $1); #58/162 from BREAKthrough (Common, about under $1); #83/202 from Sword & Shield (Common, about under $1); #092/165 from 151 (Common, about under $1); #102/162 from Temporal Forces (Common, about under $1); #55/198 from Chilling Reign (Common, about under $1); #064/196 from Lost Origin (Common, about under $1); #123/217 from Ascended Heroes (Common, about under $1); #054/94 from Phantasmal Flames (Common, about under $1); #048/88 from Perfect Order (Common, about under $1).

The collector number printed at the bottom of the card is the reliable way to tell them apart.