Answering the question about what you get with the Premium rifles is an easy one.
The Kimber is hand fitted to the stock and hand bedded, this attention to detail is what you're paying for.
I have several Kimbers, ranging from the top of the line down to the Classic. I do not own a Hunter model, but do have Super America, Select grade, Talkeetna and Montana. I cannot fault any for fit and finish. I did have one with a bad chamber job, but polishing it cured it's woes.
Of the 13 I own, all are excellent shooters.
I have a few old "L" series Sako rifles and when new they were about 3 months wages for my Dad, so very expensive. They were/are one of the most accurate guns out of the box, again, you are paying for hand fitting and attention to detail.
Cheers.