To add to Pvt. Grichmann's answer, it seems that, as far as experience goes:
Some types of trade goods can be produced in multiples. It is possible to get up to three crafts from a single resource. The chance of multiples is increased with more experience in the craftsdwarf skill.
The wiki however is amiss on what trade goods can be produced in multiples. If one were to find what those items were, you could get more value for the same resource.
Feeling dwarfy, however, I've done some experiments regarding this subject, and I found that Goblets/Mugs are produced in a 3:1 ratio and that Crafts are produced in a 2:1 ratio. The !!SCIENCE!! behind is explained here. The ratios are not dependent on skill, as stated before and as suggested by my research.
In regards to actual trading, there is also the Fun problem of trading wood items to elven caravans...
There are also weight concerns to be addressed (although, as far as these things go, they aren't all that heavy). Assuming the same material is used for all items, Jewelry (Earring, Ring, Bracelet, Amulet) all range below
50 * Density. Figurines, Crowns and Toys are in the
100 range. The heaviest craft you can make are Totems (
500), followed by Instruments (
400) and Scepters (
Having lighter items will allow to load the caravan more, hence you can buy more from the caravan, with the disadvantage the caravan will take more time to load, probably spending months loading the items until it eventually leaves.
Lastly, there are also the trade agreements you can make with your dwarven civilization, through the outpost liaison.
Items indicated in the trade agreement (accessible through the "View civilizations" menu and while you draft it with the liaison) have a relative increase in selling price. My experience indicates that it can go up to as much as 250%.
Also, although the items requested by the liaison are random in nature and may not be possible to make with the resources present in the map (such as a crystal glass piccolo instruments), more often than not, one or two of those tend to be specific crafts (in the sense of class, not material).
Summing up everything that was said so far, the gaming reasons that can affect your decision in what crafts to make are the following:
- Noble's demands
- Wood and Elves
- Weight and loading/unloading time
- Increased value to specific crafts in trade agreements
- Possibility of making more items with the same resource