If we've learned any lessons from Mythic Eldrazi in Standard, it is that they will start with a conservative price tag, then in time become financial skyscrapers while they're still legal in Standard. The power is obvious, but almost too hard to "pull off" as to be too abstract for investors and players at first. But with its first big swing into Modern season, and catching on big-time in Standard, it will likely surge to $30, $40 or even $50. The very likely Eldrazi support coming in Oath of the Gatewatch will further boost the power of this card in Standard. This seems, to me, to be the most classic of the new Eldrazi, and certainly competes with the old Ulamog.
Non-foils have bottomed out (after release hysteria) at $15 right now, and are climbing fast, and have absolutely no reason to stop before hitting $25 apiece. I suspect that after a couple months of showing up in many high-profile Standard and Modern builds, it will climb to $40. So $40 is my proposed target for selling any speculated non-foil Ulamog, the Ceaseless Hungers, any time before rotation out of Standard.
Foils will command $150-$200 apiece 3-4 years from now. Those are great long-term, low-risk, medium-return, large-granulation specs.