Have you tried to get prices from some of the holiday transfer companies ?
Hotels4u do very cheap transfers to Magaluf, try looking online.

Robert

You can get Line 1 from the airport to Palma then change for Magaluf.
In the arrivals hall there is an information kiosk (marked C for info in Catalan) and a meeting point. Right opposite is an exit door.
Walk thru door and continue ahead until you reach the pedestrian crossing, just across and on your right is the stop for line 1.
Take the bus to the Plaza Espania (Placa Espanya in Catalan), watch the electronic sign inside the bus for "Proxima Parada Placa Espanya" (Next Stop Plaza Espania) and get off there. Fare is around 1.9 Euros, takes about 15 mins.
As you exit the bus there is the escalator down to the train/bus station, go down and walk to the right and down again. Check the board for the stand number for bus to Magaluf. Fare around 2 to 3 Euros. You buy tickets on the bus, ignore the ticket m/c's.

Hotels4u are quoting £13 per person return by coach direct from airport to hotel in Magaluf. Less hassel that way or taxis are pre bookable at around 36 euro each way. Thats around £32 each way

Robert