Metro moved from Piantini almost one year ago and is much further now.....past where all the cabanas are located. It's 500 pesos to Zone Colonial, so I would imagine it would be near 1500 to the airport now.the bus station is in piantini next to plaza central. by using uber it should cost you no more than 1000 pesos during high traffic times and around 700-800 pesos during normal times. My apartment is near there so i use uber all the time for my airport runs.
you can also open the uber app and it will give you an estimate of the journey.