Cheapest priced copy (Edge of Eternities Commander): $0.49 at Card Kingdom, near mint, their price list as of .
Lux Artillery 
Artifact · Rare · Edge of Eternities Commander · #140
Whenever you cast an artifact creature spell, it gains sunburst. (It enters with a +1/+1 counter on it for each color of mana spent to cast it.)
At the beginning of your end step, if there are thirty or more counters among artifacts and creatures you control, this artifact deals 10 damage to each opponent.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
3 printings · $0.49 to $2.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Edge of Eternities Commander | 140 | Rare | $0.49 | — |
| Phyrexia: All Will Be One Commander | 27 | Rare | $0.49 | $0.99Out of stock |
| Phyrexia: All Will Be One Commander | 41 | Rare | $0.59 | $2.49Out of stock |
2 rulings from Wizards of the Coast
- 4 February 2023Lux Artillery's last ability will check if there are thirty or more counters among artifacts and creatures you control as your end step begins. If there aren't, the ability won't trigger at all. If there are, the ability will check again as it tries to resolve. If the number of counters among artifacts and creatures you control has fallen below thirty, the ability won't do anything.
- 4 February 2023If the artifact creature already has sunburst (or if you control multiple copies of Lux Artillery), each instance of sunburst works separately.