Well,

a) did you pay your Elixir contractors more than you would pay a Java contractor for similar work?

but also...

b) scarcity isn't the only factor in price. Erlang/Elixir developers are scarce, but Erlang/Elixir jobs are also scarce. You need both demand and scarcity to raise prices. Also, it doesn't cost much to turn a willing, good developer into an Erlang/Elixir developer; substitute goods reduce the impact of scarcity.

also c) if you found contractors, but not employees, maybe you weren't willing to pay enough... So maybe the price is higher than you thought?