Look into purchasing those Colombian flights outside of Colombia. At one point, in order to encourage (safe) tourism, the Colombian government was subsidizing flights for foreigners that were purchased outside the country.

Avianca (www.avianca.com) used to have really good prices on 3-7 flight packages to, from and within the country. Try to find an agent in Panama City. As a travel hub for the hemisphere and the busiest connection for Columbia, they had many great packages when I was there.

Good luck!