Every job will be different because it will depend upon how your electric is set up to begin with. I had to put a 100amp sub panel in my garage, so I could put in 2 NEMO 14-50's. I highly recommend doing 2 at the same time if you have a 2 car garage of course. Set yourself up for any future vehicles. I used Kreder Electric out of New Providence. (908) 447-0895.
I agree with GreenDarren, everybody has a different setup so cost will vary. But I went with Mike from Gladiator Electric. I had received a few quotes before using him and he was very professional and knew what he was doing. I installed a HPWC with a NEMA 14-30 as a back-up.