The “value” of an item listed in the rulebook is based on the economy of the region. For example, The Hub, the center of trade for northern California uses special bottle caps as its form of currency. Trading values within The Hub and the region are based on the bottle cap economy, which is basically The Hub’s economy. Most cities have their own dollars or what have you, but, throughout northern California, most currencies can be changed into caps (at different exchange rates, usually based on a combination of politics and the individual trading abilities and resources of the city in question. Vault City, LA, and NCR have the strongest economies, so their currencies are near the value of caps. Most merchants within cities will accept whatever dollar offered, but where the dollar comes from may affect the item’s price.
Most merchants (and regular people) will trade, but this of course involves the barter skill. Purchasing and trade prices are therefore influenced by three main factors:(1) the region’s market price (the rulebook value, usually), (2) the currency(ies) involved, and (3) the bartering skills of the PC and NPC.
I use the California examples, here, because I don’t want to spoil the roleplaying experience by simply telling you what the economy of the Colorado/New Mexico region is. That would be boring. If you want to know, you’ll have to ask an NPC.
So, there are Pueblos (which is what Pueblo, Trinidad, and Raton mostly use), chips, and whatever Heaven’s Alliance uses.