Ad Nauseam is a Modern Combo deck that has really spread its wings in the past two years.
The component pieces saw spikes back in early 2014, and have been correcting downward since that time. This deck is looking more and more competitive with time and with the recent banning of Splinter Twin in Modern, combo players are flocking to Ad Nauseam:
Ad Nauseam can be purchased for around $5 right now, though that is quickly evaporating. They are solid pickups, but I think the mid-term ceiling on Ad Nauseam is around $12. I also think a reprint is certain in Modern Masters 2017.
Foils were briefly $40 back in the 2014 spike, and can be found around $10 apiece right now: the recent price activity is only now filtering into the Foil price. Foil Ad Nauseams are where I am placing my largest bet. Foils are an easy $25 apiece in a month or two, and possibly $40 in that time, and they have a good long-term outlook unless Ad Nauseam gets banned in Modern... which is a possibility, but it's certain not to happen for at least many months. This is a popular deck, but it is not, yet, warping the format.
Some significant pieces of this deck are also spiking alongside Ad Nauseam.
The first is Phyrexian Unlife:
These are about to spike. Get ahead of the buyout. These will spike to $6 apiece, then land around $3, the price-gain will stick far better this time than the spike back in 2014. I think the new exposure will also spur some R&D on this card, possibly producing other weird uses. Additionally, future cards could easily combo with Phrexian Unlife.
The alternative combo piece to Phyrexian Unlife for Ad Nauseam is Angel's Grace, which saw a reprinting in the original Modern Masters. The reprint price suppression has long since worn off on Angel's Grace, plus it's seeing a boom in demand due to the resurging popularity of Ad Nauseam builds. Further, Angel's Grace is more versatile and sees plays in other competitive Modern archetypes besides Ad Nauseam, namely Zoo:
These Foils will be very hot. The art screams for a Foil finish. Foils will jump to $12 within a few weeks, and $20 within a couple years. I'm focusing on Foils, they have been neglected by speculation since their reprint. Not for long.
Consider, also, Lotus Bloom, which shows up in every single Ad Nauseam build I've seen, as a 4-of:
Reprinted in Modern Masters 2013, this too has fully shed its reprint blues and is just waiting for a nudge upwards. Ad Nauseam delivers. Lotus Bloom is by no means required for this deck, but it is extremely well tailored to the 5-6 converted mana cost required for combo ignition, and shows up in every single winning decklist I have come across. This can advance the combo by 1, 2 or even 3 turns in opening hands.
These will be reprinted, but demand on these is Eternal, and I would actually be suprised at a reprint in the next round of Modern Masters, because it's from early in Modern (which was focused upon heavily in the original Modern Masters) and already got a successful deflating in price. Whether Wizards feels compelled to deflate this again, come 2017, is a function of how successfully this gains value in the interim.
Non-Foil Lotus Blooms are headed from $4 to $8, these are great pick-ups. As always, go for the originals (Time Spiral) if comparable in price and condition. Foils are headed from $7 to $20, and have a fantastic long-term outlook. I would focus on original Time Spiral Foils, grab a playset and wait a few months, or a few years...
...they'll bloom, no worries.