Cheapest priced copy (Commander 2017): $0.49 at Card Kingdom, near mint, their price list as of .
Steel Hellkite 
Artifact Creature — Dragon · 5/5 · Rare · Foundations · #681
Flying
{2}: This creature gets +1/+0 until end of turn.
{X}: Destroy each nonland permanent with mana value X whose controller was dealt combat damage by this creature this turn. Activate only once each turn.
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
16 printings · $0.49 to $11.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War Commander | 163 | Rare | $0.79 | — |
| Commander 2014 | 273 | Rare | $0.59 | — |
| Commander 2017 | 225 | Rare | $0.49 | — |
| Commander 2018 | 224 | Rare | $0.59 | — |
| Commander 2021 | 266 | Rare | $0.49 | — |
| Commander Legends: Battle for Baldur's Gate | 874 | Rare | $0.49 | — |
| Commander Anthology Volume II | 222 | Rare | $0.49 | — |
| Commander Masters | 975 | Rare | $0.49 | — |
| Foundations Commander | 289 | Rare | $0.49 | — |
| Foundations | 681 | Rare | $0.49 | — |
| Murders at Karlov Manor Commander | 239 | Rare | $0.49 | — |
| Year of the Dragon 2024 | 4 | Rare | — | $11.99 |
| Scars of Mirrodin Promos | 205★ | Rare | — | $0.99 |
| Starter Commander Decks | 278 | Rare | $0.49 | — |
| Scars of Mirrodin | 205 | Rare | $0.69 | $7.99 |
| Tarkir: Dragonstorm Commander | 327 | Rare | $0.49 | — |
9 rulings from Wizards of the Coast
- 8 November 2024The mana value of a permanent is determined solely by the mana symbols printed in its upper right corner, unless it's copying something else (see below). The mana value is the total amount of mana in that cost, regardless of color. For example, a card with mana cost {3}{U}{U} has mana value 5.
- 8 November 2024If a nonland permanent has no mana symbols in its upper right corner (because it's a token that's not copying something else, for example), its mana value is 0.
- 8 November 2024Steel Hellkite's last ability destroys only nonland permanents whose mana value is exactly equal to X, and only those controlled by players who have been dealt combat damage by Steel Hellkite this turn.
- 8 November 2024If the mana cost of a permanent includes {X}, X is 0 for the purpose of determining its mana value.
- 8 November 2024In all cases, ignore any alternative costs or additional costs (such as kicker) paid when the permanent was cast.
- 8 November 2024If a permanent is copying something else, its mana value is the mana value of whatever it's copying.
- 8 November 2024It doesn't matter who controlled those permanents at the time Steel Hellkite dealt combat damage, or if those permanents were even on the battlefield at that time.
- 8 November 2024You may activate the last ability even if Steel Hellkite hasn't dealt combat damage to any players that turn. If you do, the ability won't do anything.
- 8 November 2024If Steel Hellkite's third ability is activated with X equal to 0, it will destroy each nonland permanent with mana value 0 the appropriate players control.