I went thru Phuket airport in February and called in to the limo counter for some current prices:
Limos - Patong 550baht, Kata Karon Cape Panwa 650, Kamala 500, Surin 450, Phuket Town 400, Khao Lak 1500, Krabi (Ao Nang) 2500.
Minibus - Patong 150, Kata Karon 180, Phuket Town 100.
ph - 076 351347-9
Okay, combine Surin and Khao Lak and you get 1950 for a limo (these are late model Camrys etc, not Mercs or Beemers), so if you ring that limo number they should be able to do it for that.
But I also got my Lak accomm Poseidon to pick me up from the airport for 1200, which suggests you should be able to cut a deal with someone for say 1600. I'd start with the car guys who hang around outside the various hotels and on the beach street.
I have some general info on Phuket and Lak at this site - http://tezzasthaiinfo.blogspot.com/2007/06/index.html