Cheapest priced copy (Commander 2013): $0.49 at Card Kingdom, near mint, their price list as of .
Plague Boiler 
Artifact · Rare · Ravnica: City of Guilds · #269
At the beginning of your upkeep, put a plague counter on this artifact.
{1}{B}{G}: Put a plague counter on this artifact or remove a plague counter from it.
When this artifact has three or more plague counters on it, sacrifice it. If you do, destroy all nonland permanents.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $0.49 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2013 | 254 | Rare | $0.49 | — |
| Ravnica: City of Guilds | 269 | Rare | $0.69 | $1.49 |
3 rulings from Wizards of the Coast
- 1 October 2005You choose whether to add or remove a counter when the second ability resolves. You can’t choose to remove a counter if there isn’t one there.
- 1 October 2005If the third ability triggers, removing a counter in response won’t stop the effect. However, somehow removing Plague Boiler from the battlefield in response would stop the effect because then you wouldn’t be able to sacrifice Plague Boiler.
- 1 October 2005The sacrifice is done on resolution of the triggered ability.