If you already have a dock, the lift, poles, wiring (depending on power location) motor, and how far you are from where they are...
A really rough estimate should be between 3500 to 5000. Only a site visit will tell you for sure.
If you already have a dock you can get away without having to install new poles. Look at the lifts that are on the attached link below. I bought a 6000# elevator lift this year and we installed it in one day. It attaches to existing poles or new whichever you need. Bmail if you need more info on this lift.
I am friend of Jimmy's (Hammertime Marine) in Deltaville too. He installed a lift for me that holds a 27ft Phoniex. He installed it in the boathouse which was tricky. He did a very professional job and I have never had a minutes trouble with it. He is a good man for the job.