Clan economics demand to be addressed somewhat seperately from the rest of the Inner Sphere. One of the things that makes the Clans so alien at a basic social level is that they are Socialist/Communist. While certain realms are socialistic in varying degrees, and some planets and settlements are communist, it is not a widespread mentality.
The resource poor and harsh conditions that formed the Clans required the most strict and efficient distribution of resources. On one hand, this created their highly stylized combat in order to minimize damage and resource loss. On the other hand, this led to a society where everyone recieves what they need to carry out their functions.
Within individual castes the Clans can be considered communist. The economic relationship between the Castes, however, is clearly socialist: higher castes have more resources, as determined by the Warrior Caste. The argument for this is that the ruling castes, Scientists and Warriors, require access to these greater resources in order to allow them to carry out their duties, and in some cases, to have the extra freedoms to do so.
This economic structure has survived and prospered for several reasons. First, the original harshness of the environments that forged the Clans demanded it. It was essential for survival to put the needs of the Clan ahead of the needs of the individual. Second, loyalty to the Clan is typically religious in it's fervor. Lastly, when necessity for survival and Clan loyalty fail as motivators, there are numerous cases where the Warrior Caste has used force to perpetuate the system.
When analysed in depth, it becomes apparent why the Clans typically disdain the wealth driven individuality of the Inner Sphere. It shows why the Merchant caste views a good bargain much as the Warrior caste views a battlefield victory. It explains how seeking individual wealth is considered odd and why clans that put an undue amount of emphasis on the Merchants are looked down upon. This explaination finally makes clear why the Clan homeworlds and occupied worlds appear drab and stark. Communism within castes, socialism as the method of distribution, and the overall strictness of the caste system itself all contribute to the Clans being a society totally alien to your typical resident of the Inner Sphere.