Perhaps I can shed some light on this subject. The Twilight 2000 rewrite is a D20 upgrade. The core rules are those from the Traveller T20 system.
Character creation will be somewhat loose. There are the four base classes for the military: Army, Navy, Air Force, and Marines. In addition there is three core classes for civilians: Professional, Craftsman and EMS. Each military core class will have subheadings representing military career specialties. The player will be able to select feats and skills based on service branch and then again based on specialty. The civilian classes do not have specialties built in, allowing the player to generate anything from a garbage collector to a brain surgeon. Once the class and specialty is decided the character goes through up to 4 “Term of Service” A term can be working, going to school or even prison. During each term the character earns XP based on assignment, promotions and awards. At the end of the term a check is made to see if the character has gone to War, or the player can voluntarily opt to go to war. After four terms the character automatically goes to war. There are no “Mustering Out” benefits as such, instead a character can generate extra gear, attribute bumps or skills. At the end of each term the XP is totaled and the character levels up. Prestige classes can be gained at relatively low levels and bring in the Special Forces training. (Or advanced specialties for civilians). Then the character is ready to start the game. The classes are nationality neutral. A characters country of origin is expressed more in terms of equipment then skills. The system allows a player to create a character which is tailored to their concept yet limits the power gamer.
As to the Purchase DC; Two systems are offered. One is simply a Trade Point. I found through playing T2K the most common form of trade is bargaining. So based on perceived need each piece of gear is assigned a point value. Its pretty straight forward, however, a good referee balances out the trade deals anyway. The second is based on money. This is more complicated since monetary systems have broken down and very few areas have an economy going again. T2K Ver 1, used a DC based on availability, the same is true of the re-write. No surprises here.
Should you ask your referee the DC for Vienna Fingers you would first have to find them. (Gather Information DC: 30 and several days, depending on where you are) Once found it becomes a matter of need vs want. The seller turns out to be an old survivalist and the Vienna Fingers a part of his food storage. He might be willing to part with them. He is short of ammo for his PZF 44, 67mm, Rocket launcher. He will trade the can of Vienna Fingers for 6 rockets. Of course a smooth talking trader might talk him down a rocket or two…Now, where to find the rockets?
Hope this is helpful.
As a side note. The T20 version of T2K does not have a projected release at this time, but it is in development.