Like most Magic: The Gathering cards, the value of Spinebiter depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (New Phyrexia)
Add Moltres EX to the mix and generating Energy becomes less of a worry
With Regenerate, you essentially set up a replacement effect in the form of a "regeneration shield", so to speak, before the Creature would be destroyed, and once that's done, Regenerate replaces the next instance of the destruction of said Creature with: tapping the Creature, removing damage from it, and removing it from combat
Best for: European buyers looking for transparent marketplace pricing
Promos rarely receive official collector numbers within mainline sets