Average HD games cost about 15-20 mil, but a high end game can cost 30mil, and a game like MGS4 can cost as much as 50-60mil
Comparatively, Wii games cost between 5-10 mil on average, with high end games costing up to 20 mil.
A cheap casual/minigame title can cost much less, like 1-3 mil, possibly lower if its not a very big game