Cheapest priced copy (Double Masters): $0.35 at Card Kingdom, near mint, their price list as of .
Myrsmith 
Creature — Human Artificer · 2/1 · Uncommon · Neon Dynasty Commander · #86
Whenever you cast an artifact spell, you may pay {1}. If you do, create a 1/1 colorless Myr artifact creature token.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
5 printings · $0.35 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Double Masters | 23 | Uncommon | $0.35 | $0.49 |
| Commander Masters | 44 | Common | $0.35 | $0.49 |
| Modern Masters 2015 | 28 | Uncommon | $0.35 | $0.49 |
| Neon Dynasty Commander | 86 | Uncommon | $0.35 | — |
| Scars of Mirrodin | 16 | Uncommon | $0.35 | $1.99 |
2 rulings from Wizards of the Coast
- 7 August 2020An ability that triggers when a player casts a spell resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
- 7 August 2020While resolving Myrsmith's ability, you can't pay more than {1} to get more than one Myr.