Tolkien's description of Dwarven commerce makes sense when applied to Khazad Dum but makes less sense in the context of Beleriand. The first thing that leaps to mind when considering vast underground mansions is where did they get their food? Trade is an obvious answer, though they no doubt grew some of their own in neighboring areas. Things must have been hard after Sauron razed Eregion and the west gate was shut.
But Beleriand was different. One can conceive of Dwarves trading with the Sindar, but once the Noldor arrived trade must have lessened because the Elves of the West were quite capable of forging their own weapons and doing their own construction.
Speculatively, since Tolkien describes the Dwarves as being somewhat insular, only those who enjoyed, or could tolerate, the company of Elves and Men would engage in trading. Others might have rarely left their cities, being content to engage in their first love -- the manufacture of goods. The love of creation, by the way, was likely inherited from Aulė.
As to the comparison of Dwarves to Jews, Tolkien did make this comparison himself. Way back before there were message boards I would surf for information on Tolkien and came upon a transcription of an interview in which he was asked about the inspiration for the Dwarves. His response, which I found almost offensive at first, was "don't they remind you of the Jews?" or something to that effect. After I got over being offended and read carefully, he was speaking of the Dwarves' "secret language" and their insular nature. I suppose he was referring to highly orthodox Jews that he might have observed, who spoke Yiddish or Hebrew, languages replete with consonants like Dwarvish, and who tended to maintain themselves separate from non-Jews. The men also favor beards.
But the similarity ends there. Historically, Jews were forced into commerce in order to have any degree of financial security or success because they were denied the right to own real property in many countries. Thus they operated businesses, shops, became bankers or lawyers. I am certain Tolkien never intended to imply that Dwarves were similar to Jews in connection with greed, which would be highly anti-semitic. He abhored anti-semitism and even refused to allow the Hobbit to be published in germany because the censors there required him to affirm that he had no Jewish blood. Rather he was speaking of cultural characteristics. I have even heard that Dwarvish was based upon Hebrew to some extent. I am not skilled in linguistics and cannot comment directly, but I note that the Dwarves' war cry "Baruk Khazad" resembles the Hebrew word "baruch" which signifies ""bless". "Bless the Dwarves" would not be an inappropriate war cry... I think, by the way, that some degree of sensitivity needs to be taken on the issue.
