Sierra's last ability triggers whenever you sacrifice a Food for any reason, not just to activate a Food's activated ability
While commons might not come to mind when you think of valuable cards, quite a few are worth a pretty penny, particularly those from older sets
Pokmon cards were released later that same year
Bilbo's Ring Celestial Armor Champion's Helm Cryptothrall Crystal Barricade Crystalline Giant Doors of Durin Dragonfire Blade Eater of Virtue Essence of Antiquity Giant's Amulet Glaring Spotlight Illvoi Light Jammer Inspirit, Flagship Vessel Jade Orb of Dragonkind Mask of Avacyn Mirror Shield Orbs of Warding Ring of Evos Isle Scion of Draco Shadowspear Shadowspear Simic Keyrune Skrelv, Defector Mite Soundwave, Superior Captain Sphinx of the Guildpact Survey Mechan Swiftfoot Boots Syr Ginger, the Meal Ender The Fire Nation Drill Walking Skyscraper Witchbane Orb
We played the first cards from this era, Uktabi Orangutan, Nekrataal, Man-o'-War and friends very heavily