If you read the rules as written, it actually creates more materials when used this way.
Fabricate's text says regarding the components:
Material Component
The original material, which costs the same amount as the raw materials required to craft the item to be created.
When you craft an item you pay one-third of the item’s price for the cost of raw materials.
Therefore if you let the 10 ft. chain be the original material, it costs three times the amount as the raw materials required to craft the item.
Thus using the 10 ft. chain as the original material, you can create a 30 ft. chain by the rules as written.
Seems to me that it's telling you that the uncrafted materials are cheaper than the finished thing, not that you use one third of the mass of the item. And in industry, raw material can't be a finished product (in fact it would mean ore, not even ingots, as raw means as found in nature "unprocessed or minimally processed". But in a RPG I would probably allow ingots).
Raw materials -> intermediate material -> finished product.
Intermediate would be the ingots, then the chain links. The chain itself can be considered an intermediate product if you're using it to make something else, or a finished product if you're just going to sell it that way.
If you start with a finished chain you can make a finished chain of the same length, and you should pay for the full finished chain that you used, since it wasn't a raw material. In fact, you could say that since the raw materials of a completed chain are worth 1/3 of the price of the chain, you're in fact destroying the first chain, making it lose two thirds of its value, then using the raw materials. Or you're just saving work.