When a spell which consumes an expensive material component fails due to counterspell, is the material component consumed?
It seems in line with the idea that a failed spell still consumes a spell slot.
So far as I can tell, as per p. 203 of the PHB,
If a spell states that a material component is consumed by the spell, the caster must provide this component for each casting of the spell.
It seems as though the material is consumed at the time of casting. The spell slot is also consumed at the time of casting, and as it is not returned on the event of failure, I'd think that the material components would not be, either.