With competitive Standard deck construction, large price swings are becoming common: Thundermaw Hellkite is soaring while Jace, Architect of Thought takes a dive and even well represented zombie staples aren't immune to Standard price volatility, declining in spite of continued play. Modern remains my favorite place for MtG speculation, at least until the season officially is underway. Thankfully for Standard investing die-hards, there are plenty of cards playable across both formats that still have some upside after seeing less play in Standard recently.
Some Safe Bets
Snapcaster Mage is still a 20$+ card on TCG, but ebay still has playsets ending under $80. I think this Mage is a decent speculation target under $20 if only because he'll stay in Standard through the Modern season. With his ability to turn a graveyard into card advantage, House Dimir is likely to increase his play while Modern finds a way to abuse him.
Cavern of Souls is another card to go after aggressively under $20. I'm sure Boros is going to love having W/R mana and uncounterable threats. Interestingly, the spread between buylist prices and TCGPlayer for Cavern is 23%. That is 10%+ better than other Standard staples (Thundermaw Hellkite 34%, Thragtusk 38%, Geist of Saint Traft 33%). Here we have a nice play into real estate that is going to see play in top decks in Modern and Standard.
Abrupt Decay is efficient removal that TCG has for 5.60$. Ebay is pricing near or slightly above that price, a bullish indicator in my book. Decay will likely see play in Modern Dredge to answer graveyard hate and is much more powerful in a format that is so much more under curve compared to today's Standard.
Restoration Angel has a home in Modern Pod decks and is perfect for a mid-range, Thragtusk heavy meta in Standard. Tcg lists just under $15 and here you could see a return to $20 with the kick in of Modern demand. Single W in the casting cost make Restoration Angel a potential star in any future Boros decks as well.
Steam Vents can be had for under $10. It is out of favor and with Modern Combo on the horizon, the chances it will stay unpopular seem low. In fact all the Pain Lands could reach Return to Ravnica hype levels depending on how popular Modern gets with a Masters release and full Wizards support.
Runechanter's Pike is a super efficient piece of equipment that will get stronger in standard as better instants are printed. With burn on the horizon in gatecrash and Dimir looking to fill up graveyards this sub $1 spec is looking like a potential double bagger even if it can't be abused in Modern, a somewhat difficult proposition considering most Swords earn a spot over the Pike.
Liliana of the Veil is listing on TCG for ~$24. A quick look at Ebay's completed listings shows she is pricing all over the place. Anytime you can pick up this mana efficient planeswalker for less than $20 you do yourself a favor. With Modern Jund looking to run four copies, and this Liliana showing up in Standard decklists she could test $30 before February.
In the world of commons and uncommons, Rancor and Tragic Slip will see play in Modern. I'd guess Tragic Slip is going to be a dollar common at some point into the Modern season 'cause no one wants to open Dark Ascension. Rancor is going to help speculators grind out profits much like Oblivion Ring has done in the past. Look to pick these up as throw-ins when possible or close deals yourself with them.
In general picking up cards that see play in multiple formats is always a good conservative approach to MtG speculation. Rarely do you have so many Modern-playable Standard staples ready to make a splash. This, with Wizards interest in the Modern format (see Modern Masters and FNM Modern support), could mean an unprecedented opportunity for speculators.
The positive catalysts should at least make grinding out 33% returns on quick flips easier. Those that like to flip to dealers should pay attention to that return as it usually represents a leg up in a card's pricing. Presently most buylist prices are within 30-35% of the dealer's sell price. Use that percentage return when trading to find snap trades. When buying cards, paying more than 33% of a buylist price is going to make a quick flip that much harder.
Until next time, happy hunting!