Economy

Neither scandium nor yttrium are in the strictest sense, "rare earths" in the often unfortunate use of this term. (The better term is "lanthanide.) Formally, although their chemistry is very similar and they are generally found in the two main lanthanide ores, they are formally transition elements, given their position in the periodic table.

Scandium is indeed rare. We're it not rare, it would replace aluminum in industry because of its remarkable properties as a metal, which are superior to those of aluminum.

Yttrium is a major fission product and can be isolated from used nuclear fuel. It has no long lived isotopes, other than ⁹⁰Y, with a half life of 64 hours and which is in secular equilibrium with ⁹⁰Sr. Thus cooling for a few weeks after isolation, and purification to remove traces of stable zirconium, it is ready for use.

Just saying...