What's the number a console needs to sell not to be a failure?

[GoldenGamer]

It needs to account for a lot of market share. 21 million is a failure when your competition sold over 100mil. It would need to sell at least 50 million, since the market is large. 21 would only be good if the highest selling console is no more than 30-40 million. Selling only 21 million is not a profit if you shipped twice as many consoles.