Elixir of Vitality 
Artifact
This artifact enters tapped.
{T}, Sacrifice this artifact: You gain 4 life.
{8}, {T}, Sacrifice this artifact: You gain 8 life.
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Cards that do something similar expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.
Omni-Cheese Pizza 99%
$0.15#14584
"{2}, {T}, Sacrifice this artifact: You gain 3 life."
+2 more matching lines
Instant Ramen 99%
$0.20#5747
"{2}, {T}, Sacrifice this artifact: You gain 3 life."
+1 more matching line
Golden Egg 99%
$0.25#7922
"{2}, {T}, Sacrifice this artifact: You gain 3 life."
+2 more matching lines
Dungeoneer's Pack 95%
$0.28#10332
"{2}, {T}, Sacrifice this artifact: You take the initiative, gain 3 life, draw a card, and create a Treasure token. Activate only as a sorcery."
+1 more matching line
Oni-Cult Anvil 84%
$0.25#6031
"{T}, Sacrifice an artifact: This artifact deals 1 damage to each opponent. You gain 1 life."
Pyxis of Pandemonium 81%
$0.28#11680
"{7}, {T}, Sacrifice this artifact: Each player turns face up all cards they own exiled with this artifact, then puts all permanent cards among them onto the battlefield."