The solution is incomplete. The wife said she came out an ANOTHER entrance. Yet we are led from the description provided there is only 1 entrance. Why couldn't the wife and her lover McQuire do it together. Her leading her husband to a pre-arranged spot, and then McQuire doing the killing. Remember they found the body together, so why could they not have killed together.

The sign translates as "$10 a piece", I am assuming that this is refers to Hong Kong Dollars which exchange at a fixed rate of HK$7.7 to 1 US$ or approximately $1.30 per chicken.