I fly Copa fairly often and buy on Copaair.com from my office in Costa Rica.

Several times lately I have found their flights quite a bit cheaper on Orbitz. I loose the 2000 mile bonus, but have paid less than 1/2 of what they were getting on their site. Their prices come down usually when Taca and them get into a battle over a route, otherwise, I would not consider them a discount for locals line.