When you play Magcargo from your hand to evolve your Active Pokémon, you may discard the top 3 cards of your deck and and then shuffle 3 basic Energy cards from your discard pile into your deck. If you do, your opponent does the same.
Attacks
40+Crushing Lava
You may discard a Fire or Fighting basic Energy card attached to Magcargo. If you discard a Fire Energy card in this way, the Defending Pokémon is now Burned. If you discard a Fighting Energy card in this way, this attack does 40 damage plus 20 more damage.
How much is Magcargo #H17/144 worth?
Magcargo #H17/144 is a Rare Holo card from Skyridge (2003) — today it trades at roughly $202.50 ungraded.
Grading changes the math on this one: a PSA 10 is valued around $5,429.14, roughly 26.8x the raw price, while a PSA 9 sits near $775.00. 593 copies have been graded to date, and 17% of them came back a 10 — worth knowing before you pay grading fees.
These figures come from nightly market-data syncs verified against completed sales. Use the chart above to see the trend before you buy or sell.