About $70 from saladita to the airport. Most taxis have a list of official rates. From the airport walk outside the airport parking lot and bargain.
Great deal, but slow. Just flag one down and get of at km 37 los Llanos.
For the big companies, get your rental ahead of time, online, if you are renting from the likes of Dollar, Eurocar etc. They will stick it to you with insurance on the ground.