Benefactor's Draught and Duelist's Heritage are both just awesome, straightforward new Commander designs.
Why are they worth so much, good reprints?
There's always going to be a certain unavoidable amount of value in the new cards as long as they're at all desirable since this is the only place to get them, and then the rest is just in solid, medium-value reprints of cards with few previous printings. Cards > $4 in each deck:
Entropic Uprising: Past in Flames, Chromatic Lantern, Burgeoning, Waste Not
Open Hostility: Iroas, God of Victory, Karplusan Forest
Stalwart Unity: Progenitor Mimic, Collective Voyage, Tempt with Discovery, Venser's Journal, Lurking Predators, Forbidden Orchard, Homeward Path
Breed Lethality: Scavenging Ooze, Ghave, Guru of Spores, Kalonian Hydra, Reveillark, Cauldron of Souls, Darkwater Catacombs
Invent Superiority: Baleful Strix, Hanna, Ship's Navigator, Master of Etherium, Solemn Simulacrum, Godo, Bandit Warlord
Plus they each have a bunch of random $1-$3 cards at current prices. They all price out at above $80 on mtggoldfish just on reprints. They've got the priced lists up on the site now:
https://www.mtggoldfish.com/articles/commander-2016-decklists
Anyway, they'll settle down to cover price, which means most of those higher-priced older cards are gonna tank.