Cheapest priced copy (March of the Machine): $5.99 at Card Kingdom, near mint, their price list as of .
Sword of Once and Future 
Artifact — Equipment · Mythic · March of the Machine Promos · #265p
Equipped creature gets +2/+2 and has protection from blue and from black.
Whenever equipped creature deals combat damage to a player, surveil 2. Then you may cast an instant or sorcery spell with mana value 2 or less from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.
Equip {2}
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $5.99 to $13.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| March of the Machine | 265 | Mythic | $5.99 | $6.99 |
| March of the Machine | 375 | Mythic | $6.99 | $9.99 |
| March of the Machine Promos | 265p | Mythic | $5.99 | $6.99 |
| March of the Machine Promos | 265s | Mythic | — | $13.99 |
5 rulings from Wizards of the Coast
- 14 April 2023You choose whether or not to cast the instant or sorcery card as the triggered ability resolves. If you do, you do so as part of the resolution of that ability. You can't wait to cast it later in the turn. Timing restrictions based on the card's type are ignored.
- 14 April 2023If you cast a card "without paying its mana cost," you can't pay any alternative costs. You can, however, pay additional costs. If the card has any mandatory additional costs, those must be paid to cast the card.
- 14 April 2023If the card has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.
- 14 April 2023The card you cast may be one you just put into the graveyard with surveil or one already in the graveyard.
- 12 January 2024When you surveil, you may put all the cards you look at back on top of your library, you may put all of those cards into your graveyard, or you may put some of those cards on top and the rest of them into your graveyard.