I don't follow the development of games on MS platform... Gears 1 cost 7 million, I'm not sure what the question is from that actually, good catch. It be because Unreal Engine 3 was created by the guys who made Gears, but I may be mistaken on that - I confuse those companies very easily as they all are the same to me. (Constantly trying to sell their engines to anyone who's willing to buy/middleware) I believe Gears worked with Unreal Engine 3, while Ubi licensed the use of Ue2.5, now this is just memory now so I could be off, but last time I checked licensing that engine isn't cheap. But I'm almost positive it couldn't have cost Ubi an near 10 million just to use that Engine.
Anyway that 1:5 ratio isn't fair actually, because it only works in a few cases, and the one case it was intended to express was only to give a rough understanding of rate of investment per dollar, the end result could be less depending on how long and how intense production is.
Also if your talking about Gears 2... then I can say that they just recycled tools to simplify production. This means the only thing they'd have to spend time on is bugs and content.