Feb 18 2012, 4:58pm
There in the second paragraph, DarkJackal.
Tolkien's view of his mythology developed during (and after) he wrote the Hobbit, and the dwarves certainly do change over the course of the story.
However, I also think that has to do with the simple fact that the dwarves are travelling from the relative peace and mundane parochialism of the Shire, to the "Wild." By the time they are in Erebor, in the heart of the Lonely mountain, their journey from the ordinary and routine life to the very center of the wild in the dragon's lair (and the center of their dwarven being, an ancestral underground hall full of treasure) is complete. So it makes narrative sense for these two different versions of the dwarves, and Thorin, to exist (and it is no accident that the dwarves originally came from "the East.")
In the kindly West, the dwarves became soft, and perhaps, as you suggest, adopted some of the habits and speech of their soft, "grocer" neighbors. In the wild East, they become hardened again, literally returning, as they do, to their heroic (mountain) roots.
In this sense, the contract is either an attempt by Thorin to appeal to his hobbit host, or an indication that the dwarves have grown a bit hobbitish. In both cases, however, the style is not what one would describe as "dwarven."
(This post was edited by Shelob'sAppetite on Feb 18 2012, 5:02pm)