Robert wrote:so would it be very expensive to take a taxi from Bogotá to Medellin? It looks like it's a couple hours away based on distance,
It will be rather expensive as it's not a couple of hours.
Bogotá to Medellin is 414 Km (260 miles) and a 8 hours trip by bus, maybe you'll save 1 or two hours by taxi..
But I think you could fly from Bogotá to Medellin or Cartagena.
AeroRepublica offers flights starting around $110 but if you don't want to bother with bad logistics, it will cost you around $200..