Rare earth material
Scandium is a rare earth metal whereas aluminum occurs in abundance.
Due to its scarcity, scandium is known to be one of the most expensive metals in the world. The price per kilogram fluctuates depending on the amount mined. It usually starts at U$4 000 and it is not abnormal to go as high as US$20 000.
This rare metal is commonly found in Russia and China however recently it has been discovered in Australia.
Scandium is not only a rare material, it is also hard to extract from the ore, hence the extremely high costs. For that reason, 3D printing pure scandium is not feasible.