Im actually more interested in Cubes where Gray Merchant of Asphodel can make meaningful appearances in two-color decks than in ones with incredibly prohibitive casting costs like that of Phyrexian Obliterator
This makes your choice of Trainer cards as flexible as necessary
These packs are about 500,- each
With some careful deck building (mostly playing some big card-draw spells you can cycle into with Unpredictable Cyclone to make sure you always have some cycling cards in hand), you should be able to mostly play your entire deck in a single turn by cycling, casting stuff (including card-draw spells) for free with Unpredictable Cyclone, drawing into more cycling cards, and cycling them to trigger Unpredictable Cyclone against and again until you've essentially cast your entire deck

Blight Mamba Blightsteel Colossus Blightwidow Burn the Impure Carrion Call Core Prowler Corpse Cur Cystbearer Fallen Ferromancer Glistener Elf Grafted Exoskeleton Happy Dead Squirrel Ichorclaw Myr Inkmoth Nexus Lost Leonin Melira, Sylvok Outcast Mindcrank Necropede Ogre Menial Pestilent Souleater Phyrexian Digester Phyrexian Hydra Phyrexian Juggernaut Phyrexian Swarmlord Phyrexian Unlife Plague Myr Priests of Norn Putrefax Razor Swine Rot Wolf Shriek Raptor Spinebiter Tangle Angler Tel-Jilad Fallen Tine Shrike Trigon of Infestation Triumph of the Hordes Vector Asp Viridian Betrayers Viridian Corrupter
The top end of the range for this card caps out at about $32, leaving plenty of room to find one for a cheaper price, especially if you're willing to settle for damaged copies, which you might find for under ten dollars, depending on how much damage you're willing to tolerate