I'm currently doing the same research in Bogotá.
Bogotá seems the best place to fly out in Colombia. Many agents here but the most experienced on motorcycle transport seem to be Girag and COPA Cargo.
Check HUs shipments by travellers: Lyncargo asked Bogotá to Miami (US) around 1000USD-ish or a bit more for the bike, ticket per person cheapest I found is 150USD-ish with BlueJet. If you want to skip all the Central-America and swine flu panic in Mexico.
From Bogotá to Panama City 800USD fixed (price was quoted just yesterday directly from Girag) - no matter how small or big bike you have. They fly to Panama City every wendsday, thursday, friday and sunday with the cargo plane. You have to bring the bike in their office one day before the flight, easy as that. I've heard some bad stories as well from other travellers, where bikes are getting a bit damaged (scratched, dented, etc) with the airport-transport, but apparently minor cases (fingers crossed on our attempt).
Another option is from Cartagena to Panama with the sailing ship (a bit cheaper, less convenient, longer, but at least you see the Carribean
Take your pick.