This cube is for simulating drafting packs, with cards being present in almost exactly the ratios of packs. The only cards not present are the fetch lands (replaced by common duals), which makes the entire cube cheaper than a box of Khans (~$100).
This cube can be built for ~$90. eBay 4x commons/uncommons as a block, buy an extra set of commons as signles, 2x each rare and 1x each mythic, and an extra set of 2x each common dual lands.
Remove any cards you think would be un-fun for draft.