Mortis said:
Well if YOU

want to include advancement that looks good.
D'oh! I had it backwards.
No, I don't really want advancement.
We can tweak the iron golem's construction...
Construction
An iron golem’s body is sculpted from 5,000 pounds of pure iron, smelted with rare tinctures and admixtures costing at least 10,000 gp. Assembling the body requires a DC 20 Craft (armorsmithing) check or a DC 20 Craft (weaponsmithing) check.
CL 16th; Craft Construct, cloudkill, geas/quest, limited wish, caster must be at least 16th level; Price 150,000 gp; Cost 80,000 gp + 5,600 XP.
Wilbur originally weighed 833 pounds, so that gives us our x pounds of pure iron.
Maybe add shrink item and secret chest to the prereqs, and drop cloudkill?
Drop craft DCs to 15?
Drop price to 50,000?