I think the estimate of game development costs tend to be misleading because a (unusually) simple game like Brain Training can be developed by a handful of developers over a couple of months whereas a more complicated game like Final Fantasy Crystal Chronicles: My Life as a King probably takes a much larger development team working for far longer.
In general, I would say it would be a good idea to estimate an average development cost of $500,000 to $1,000,000 for a WiiWare/XBox Live Arcade game and $1,000,000 to $2,000,000 for a budget priced disc game. At the same time I would expect developers would be happy if they recovered twice the development cost for these games being that their marketing costs are low. Assuming $5 to $10 revenue from an WiiWare/XBox Live Arcade game (and revenue of $10 to $20 for a budget priced disc based game) developers would be (very) happy with sales in the 100,000 to 400,000 range.
