Double Masters is an artifact-focused Masters set containing 40 mythic and 121 rare reprint cards throughout Magic's history. Also, Double Masters includes sought-after Competitive Commander (cEDH) staples. Prices for many cEDH playable cards increased during 2020. However, Double Masters has reduced prices to their lowest in over a year for some cEDH staples. All Double Masters price predictions mentioned are for ordinary, non-foil versions. 

Mythic Staples

Mana Crypt is a zero-mana ramp artifact that slots into any deck. The drawback of potentially losing 3 life is less significant in cEDH. Mana Crypt enables threats and combo kills. Any player interested in improving the competitiveness of an EDH deck will want one. Mana Crypt's price has not been below $90.00 since January 2018. Due to two reprints in 2020, now could be the best time to grab a copy around $90.00.

Chrome Mox is another zero-mana ramp artifact. Unlike Mana Crypt, Chrome Mox provides one colored mana based on what card gets imprinted. Players building cEDH decks will likely include Chrome Mox alongside Mana Crypt for additional mana generation. Chrome Mox's price hovered around $40.00 in 2019 but increased over time. It would not be unreasonable for Chrome Mox's price to drop to about $35.00. 

Mox Opal is a zero-mana ramp artifact with more restrictions than Chrome Mox or Mana Crypt. Activating Mox Opal for mana requires a player to control at least two additional artifacts. While Mox Opal is not an ideal inclusion in all cEDH decks, it does see play in top-tier decks, including Kraum, Ludevic's Opus/Tymna the Weaver, and Kess, Dissident Mage. Mox Opal's price dropped to about $50.00 after its Modern banning. With the inclusion in Double Masters, Mox Opal's price may land between $30.00 and $35.00.

Trinisphere slots well in stax decks that attempt to slow down and disrupt an opponent's game plan. Disruptive cEDH commanders such as Brago, King Eternal, Derevi, Empyrial Tactician and Hapatra, Vizier of Poisons may want a copy of Trinisphere. Double Masters is only the second set containing non-foil copies of Trinisphere. Prices for Trinisphere could fall considerably due to supply increases. A floor price for Trinisphere is probably close to $12.00 or a 60% discount from the previous average market price.   

Dark Confidant is a powerhouse in cEDH decks featuring Tymna the Weaver, Kess, Dissident Mage, Najeela, the Blade-Blossom, and Zur the Enchanter. Since most spells in these decks are three mana or less, Dark Confidant is an excellent card advantage engine. Dark Confidant's price has maintained around $50.00 throughout 2020. Considering its playability in multiple formats, any amount between a 40% to 50% discount seems like a good buy.

Force of Will is a counterspell that has shaped competitive play for years. This card is in almost every blue commander cEDH decklist. Also, Force of Will is a top 25 blue card on EDHREC. The alternate casting cost of countering a spell without spending mana makes it an ideal inclusion. The price of Force of Will has stayed above $80 since 2018. The price of Force of Will could dip under $80 due to the average amount of mythic cards per booster box.  

Rare Staples

Walking Ballista is a combo finisher with Heliod, Sun-Crowned, Animar, Soul of Elements and Naru Meha, Master Wizard. Any cEDH deck that can produce infinite mana could use Walking Ballista as a win condition. The average price for Walking Ballista has teetered between $20 and $30 since January 2020. Prices for Walking Ballista may hover between $12.00 and $15.00. 

Ethersworn Canonist is a white artifact creature with a stax effect. Like Trinisphere, Ethersworn Canonist finds a home in Brago, King Eternal and Derevi, Empyrial Tactician. The price of Ethersworn Canonist has stayed above $6 due in part to supply level. With its inclusion in Double Masters, Ethersworn Canonist's price should drop 65% to 75%.   

For one green mana, Noble Hierarch produces three colors and provides an exalted trigger. Noble Hierarch slots well in four and five-color cEDH decks. Commanders like Najeela, the Blade-Blossom, Kenrith, the Returned King and Thrasios, Triton Hero/Tymna the Weaver may want to include Noble Hierarch. Also, Noble Hierarch synergizes with Chulane, Teller of Tales. Since Noble Hierarch is rare in Double Masters, the average price could fall to around $15.00. 

Rolling Earthquake is a little-known card initially printed in Portal Three Kingdoms. It saw one reprint as a foil version in From The Vault: Annihilation. Commanders such as Niv-Mizzet, Parun, Godo, Bandit Warlord and Elsha of the Infinite may want Rolling Earthquake. Historical prices for Portal Three Kingdoms have averaged around $65.00, while FTV versions have sold for about $13.00. While the card suffers from supply issues, it may also be unknown to many EDH players. Rolling Earthquake is arguably a better deck inclusion than Earthquake, a top 50 red card on EDHREC. The Double Masters price for Rolling Earthquake is about $2.00. Rolling Earthquake could be a sleeper buy for cEDH and EDH players at a price under $5.00.

Timing Prices and Purchases

In the article Five Financial Facts about Double Masters, Cassie LaBelle says the best time to buy Masters set singles is release weekend (August 6th-7th) or late December. I concur with LaBelle that release weekend is an excellent opportunity due to dramatic supply increases in the secondary market. There is often a race to the bottom on prices as individuals open booster boxes and sell singles. Any of the cEDH mythic staples mentioned, except for Trinisphere, may rebound in price after Double Masters' release. Trinisphere suffered from a lack of supply and is less played than other mythic cards. I plan to purchase the missing pieces for a Godo, Bandit Warlord cEDH deck. 

As for rare staples, Walking Ballista is the most common deck inclusion among the group. I believe Rolling Earthquake is underutilized in EDH and a steal for a few dollars. My prediction is that both of these cards will increase in price slowly upon release. Regardless of when players acquire cards from Double Masters, the set has brought significant price reductions for sought after cEDH staples.