Graded cards can have stronger resale value depending on the grade and card popularity
Schematic serialized Retro Artifact foil: $1,000 to $2,500 Retro Artifact foil: $40 to $70 Schematic Retro Artifact non-foil: $30 to $40 Minds Eye Popular in the Commander because its a multiplayer format, Minds Eye allows players to pay one mana on each opponents turn to draw a card
Using penny sleeves inside binder pages provides an extra barrier against scratches and helps keep dust or fingerprints off the card surface
this was even more important back in the day before we regularly put token cards in booster packs)
especially since the cost to Proliferate (he gets tapped, you need to sacrifice a Creature, and Proliferation at Sorcery-speed) is rather steep
Note that you get counters put on the attacking creature, not an until end of turn pumping