STAR RATINGS:
When it comes to star ratings, price is not a factor. The plain and simple question is, "how good is this ship?" Most of the factors considered have to do with age, is in older ships tend to rate lower, but not if the furnishings and finishings are like new. Small cabins, lack of balcony cabins, ho-hum food, bad service, and below average entertainment will knock a ship down when it comes to the number of stars.
However, please don't use stars alone as your indicating factor, in fact, don't even use it as your first determinator. If you know what to expect out of a three star ship, and you get a great price on the cruise fare. Hurray! You are going to have a great cruise. So, what is more important is the "value" factor (outlined below). Because what you get for your money is more important than how much you pay!