If they lump Instant and Sorceries together, man, they're burning through types pretty fast. That just leaves Enchantments, Planeswalkers, and Creatures (though Creatures are a deep enough well that you could do a few runs without hitting repeats).
Getting pretty quickly to Masterpiece repeats is something that they'd be fine with I'd think. Different fancy versions of a highly played card should still fetch a high price even if there's already a masterpiece version of it out there.