you're not considering everything.
retailers typically negotiate contracts that if they buy XXX number of units and only sell a fraction of them sell then the publisher is on the hook to buy the remainder back. BUT, the publisher still has to pay the distribution and royalty cost of the original printing. so if the publisher overestimates demands it can significantly reduce or even eliminate all revenues on the game.
point is even if 100k units are sold,... if the publisher printed100k they make a profit,. if the publisher printed 200k then they probably made no revenue, and if they printed 500k they have negative revenue. it's a risk and potentially a costly one.
remember THQ? over estimating the UDraw demand on the HD consoles was the number one loss maker contributing to their bankruptcy.
